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//! A dynamic array based on a 2-level rotated array. //! //! See <a href="https://github.com/senderista/rotated-array-set/blob/master/README.md">the `rotated-array-set` README</a> for a detailed discussion of the performance //! benefits and drawbacks of an equivalent data structure. #![doc(html_root_url = "https://docs.rs/rotated-vec/0.1.0/rotated_vec/")] #![doc(html_logo_url = "https://raw.githubusercontent.com/senderista/rotated-array-set/master/img/cells.png")] use std::mem; use std::cmp::{min, Ordering}; use std::fmt::Debug; use std::hash::{Hash, Hasher}; use std::iter::{DoubleEndedIterator, ExactSizeIterator, FromIterator, FusedIterator}; use std::ops::{Index, IndexMut}; /// A dynamic array based on a 2-level rotated array. /// /// This is roughly a drop-in replacement for `Vec`, except that there is no /// deref to a slice, so underlying slice methods are unavailable. Many of /// the most useful slice methods have been ported. /// /// # Examples /// /// ``` /// use rotated_vec::RotatedVec; /// /// // Type inference lets us omit an explicit type signature (which /// // would be `RotatedVec<i32>` in this example). /// let mut vec = RotatedVec::new(); /// /// // Push some integers onto the vector. /// vec.push(-1); /// vec.push(6); /// vec.push(1729); /// vec.push(24); /// /// // Pop an integer from the vector. /// vec.pop(); /// /// // Insert an integer at a given index. /// vec.insert(1, 0); /// /// // Remove an integer at a given index. /// vec.remove(1); /// /// // Change an integer at a given index. /// vec[1] = 0; /// /// // Iterate over everything. /// for int in &vec { /// println!("{}", int); /// } /// ``` #[derive(Debug, Clone)] pub struct RotatedVec<T> { data: Vec<T>, start_indexes: Vec<usize>, } /// An iterator over the items of a `RotatedVec`. /// /// This `struct` is created by the [`iter`] method on [`RotatedVec`][`RotatedVec`]. /// See its documentation for more. /// /// [`RotatedVec`]: struct.RotatedVec.html /// [`iter`]: struct.RotatedVec.html#method.iter #[derive(Debug, Copy, Clone)] pub struct Iter<'a, T: 'a> { container: &'a RotatedVec<T>, next_index: usize, next_rev_index: usize, } impl<'a, T> Iter<'a, T> where T: Copy + Default + Debug, { #[inline(always)] fn assert_invariants(&self) -> bool { assert!(self.next_index <= self.container.len()); assert!(self.next_rev_index <= self.container.len()); if self.next_rev_index < self.next_index { assert!(self.next_index - self.next_rev_index == 1); } true } } /// An iterator over the items of a `RotatedVec`. /// /// This `struct` is created by the [`iter_mut`] method on [`RotatedVec`][`RotatedVec`]. /// See its documentation for more. /// /// [`RotatedVec`]: struct.RotatedVec.html /// [`iter_mut`]: struct.RotatedVec.html#method.iter_mut #[derive(Debug)] pub struct IterMut<'a, T: 'a> { container: &'a mut RotatedVec<T>, next_index: usize, next_rev_index: usize, } impl<'a, T> IterMut<'a, T> where T: Copy + Default + Debug, { #[inline(always)] fn assert_invariants(&self) -> bool { assert!(self.next_index <= self.container.len()); assert!(self.next_rev_index <= self.container.len()); if self.next_rev_index < self.next_index { assert!(self.next_index - self.next_rev_index == 1); } true } } /// An owning iterator over the items of a `RotatedVec`. /// /// This `struct` is created by the [`into_iter`] method on [`RotatedVec`][`RotatedVec`] /// (provided by the `IntoIterator` trait). See its documentation for more. /// /// [`RotatedVec`]: struct.RotatedVec.html /// [`into_iter`]: struct.RotatedVec.html#method.into_iter #[derive(Debug, Clone)] pub struct IntoIter<T> { vec: Vec<T>, next_index: usize, } impl<T> RotatedVec<T> where T: Copy + Default + Debug, { /// Makes a new `RotatedVec` without any heap allocations. /// /// This is a constant-time operation. /// /// # Examples /// /// ``` /// #![allow(unused_mut)] /// use rotated_vec::RotatedVec; /// /// let mut vec: RotatedVec<i32> = RotatedVec::new(); /// ``` pub fn new() -> Self { RotatedVec { data: Vec::new(), start_indexes: Vec::new(), } } /// Constructs a new, empty `RotatedVec<T>` with the specified capacity. /// /// The vector will be able to hold exactly `capacity` elements without /// reallocating. If `capacity` is 0, the vector will not allocate. /// /// It is important to note that although the returned vector has the /// *capacity* specified, the vector will have a zero *length*. /// /// # Examples /// /// ``` /// use rotated_vec::RotatedVec; /// /// let mut vec = RotatedVec::with_capacity(10); /// /// // The vector contains no items, even though it has capacity for more /// assert_eq!(vec.len(), 0); /// /// // These are all done without reallocating... /// for i in 0..10 { /// vec.push(i); /// } /// /// // ...but this may make the vector reallocate /// vec.push(11); /// ``` pub fn with_capacity(capacity: usize) -> RotatedVec<T> { let start_indexes_capacity = if capacity > 0 { Self::get_subarray_idx_from_array_idx(capacity - 1) + 1 } else { 0 }; RotatedVec { data: Vec::with_capacity(capacity), start_indexes: Vec::with_capacity(start_indexes_capacity), } } /// Returns a reference to the value in the array, if any, at the given index. /// /// This is a constant-time operation. /// /// # Examples /// /// ``` /// use rotated_vec::RotatedVec; /// /// let vec: RotatedVec<_> = vec![1, 2, 3].into(); /// assert_eq!(vec.get(0), Some(&1)); /// assert_eq!(vec.get(3), None); /// ``` pub fn get(&self, index: usize) -> Option<&T> { if index >= self.data.len() { return None; } let real_idx = self.get_real_index(index); Some(&self.data[real_idx]) } /// Returns a mutable reference to the value in the array, if any, at the given index. /// /// This is a constant-time operation. /// /// # Examples /// /// ``` /// use rotated_vec::RotatedVec; /// /// let mut vec: RotatedVec<_> = vec![1, 2, 3].into(); /// assert_eq!(vec.get_mut(0), Some(&mut 1)); /// assert_eq!(vec.get_mut(3), None); /// ``` pub fn get_mut(&mut self, index: usize) -> Option<&mut T> { if index >= self.data.len() { return None; } let real_idx = self.get_real_index(index); Some(&mut self.data[real_idx]) } /// Swaps two elements in the vector. /// /// This is a constant-time operation. /// /// # Arguments /// /// * a - The index of the first element /// * b - The index of the second element /// /// # Panics /// /// Panics if `a` or `b` are out of bounds. /// /// # Examples /// /// ``` /// use rotated_vec::RotatedVec; /// /// let mut vec: RotatedVec<_> = vec!["a", "b", "c", "d"].into(); /// vec.swap(1, 3); /// assert_eq!(vec, vec!["a", "d", "c", "b"].into()); /// ``` pub fn swap(&mut self, a: usize, b: usize) { self.data.swap(a, b); } /// Returns the number of elements the vector can hold without /// reallocating. /// /// # Examples /// /// ``` /// use rotated_vec::RotatedVec; /// /// let vec: RotatedVec<i32> = RotatedVec::with_capacity(10); /// assert_eq!(vec.capacity(), 10); /// pub fn capacity(&self) -> usize { self.data.capacity() } /// Reserves the minimum capacity for exactly `additional` more elements to /// be inserted in the given `RotatedVec<T>`. After calling `reserve_exact`, /// capacity will be greater than or equal to `self.len() + additional`. /// Does nothing if the capacity is already sufficient. /// /// Note that the allocator may give the collection more space than it /// requests. Therefore, capacity can not be relied upon to be precisely /// minimal. Prefer `reserve` if future insertions are expected. /// /// # Panics /// /// Panics if the new capacity overflows `usize`. /// /// # Examples /// /// ``` /// use rotated_vec::RotatedVec; /// /// let mut vec: RotatedVec<_> = vec![1].into(); /// vec.reserve_exact(10); /// assert!(vec.capacity() >= 11); /// ``` pub fn reserve_exact(&mut self, additional: usize) { self.data.reserve_exact(additional); } /// Reserves capacity for at least `additional` more elements to be inserted /// in the given `RotatedVec<T>`. The collection may reserve more space to avoid /// frequent reallocations. After calling `reserve`, capacity will be /// greater than or equal to `self.len() + additional`. Does nothing if /// capacity is already sufficient. /// /// # Panics /// /// Panics if the new capacity overflows `usize`. /// /// # Examples /// /// ``` /// use rotated_vec::RotatedVec; /// /// let mut vec: RotatedVec<_> = vec![1].into(); /// vec.reserve(10); /// assert!(vec.capacity() >= 11); /// ``` pub fn reserve(&mut self, additional: usize) { self.data.reserve(additional); } /// Shrinks the capacity of the vector as much as possible. /// /// It will drop down as close as possible to the length but the allocator /// may still inform the vector that there is space for a few more elements. /// /// # Examples /// /// ``` /// use rotated_vec::RotatedVec; /// /// let mut vec = RotatedVec::with_capacity(10); /// vec.extend([1, 2, 3].iter().cloned()); /// assert_eq!(vec.capacity(), 10); /// vec.shrink_to_fit(); /// assert!(vec.capacity() >= 3); /// ``` pub fn shrink_to_fit(&mut self) { self.data.shrink_to_fit(); } /// Shortens the vector, keeping the first `len` elements and dropping /// the rest. /// /// This is an `O(√n)` operation. /// /// If `len` is greater than the vector's current length, this has no /// effect. /// /// Note that this method has no effect on the allocated capacity /// of the vector. /// /// # Examples /// /// Truncating a five element vector to two elements: /// /// ``` /// use rotated_vec::RotatedVec; /// /// let mut vec: RotatedVec<_> = vec![1, 2, 3, 4, 5].into(); /// vec.truncate(2); /// assert_eq!(vec, vec![1, 2].into()); /// ``` /// /// No truncation occurs when `len` is greater than the vector's current /// length: /// /// ``` /// use rotated_vec::RotatedVec; /// /// let mut vec: RotatedVec<_> = vec![1, 2, 3].into(); /// vec.truncate(8); /// assert_eq!(vec, vec![1, 2, 3].into()); /// ``` /// /// Truncating when `len == 0` is equivalent to calling the [`clear`] /// method. /// /// ``` /// use rotated_vec::RotatedVec; /// /// let mut vec: RotatedVec<_> = vec![1, 2, 3].into(); /// vec.truncate(0); /// assert_eq!(vec, vec![].into()); /// ``` /// pub fn truncate(&mut self, len: usize) { if len >= self.len() { return } // conceptually, we drop all subarrays after the truncated length, // then un-rotate the new last subarray, then drop any remaining elements. self.unrotate_last_subarray(); // drop subarrays after truncated length let last_subarray_idx = Self::get_subarray_idx_from_array_idx(self.len() - 1); self.start_indexes.truncate(last_subarray_idx + 1); // truncate data array self.data.truncate(len); } /// Gets an iterator that visits the values in the `RotatedVec` in order. /// /// # Examples /// /// ``` /// use rotated_vec::RotatedVec; /// /// let vec: RotatedVec<usize> = vec![1, 2, 3].into(); /// let mut iter = vec.iter(); /// assert_eq!(iter.next(), Some(&1)); /// assert_eq!(iter.next(), Some(&2)); /// assert_eq!(iter.next(), Some(&3)); /// assert_eq!(iter.next(), None); /// ``` pub fn iter(&self) -> Iter<T> { Iter { container: self, next_index: 0, next_rev_index: if self.len() == 0 { 0 } else { self.len() - 1 }, } } /// Gets a mutable iterator that visits the values in the `RotatedVec` in order. /// /// # Examples /// /// ``` /// use rotated_vec::RotatedVec; /// /// let mut vec: RotatedVec<usize> = vec![1, 2, 3].into(); /// let mut iter = vec.iter_mut(); /// let mut current_elem = None; /// current_elem = iter.next(); /// assert_eq!(current_elem, Some(&mut 1)); /// *current_elem.unwrap() = 2; /// current_elem = iter.next(); /// assert_eq!(current_elem, Some(&mut 2)); /// *current_elem.unwrap() = 3; /// current_elem = iter.next(); /// assert_eq!(current_elem, Some(&mut 3)); /// *current_elem.unwrap() = 4; /// assert_eq!(iter.next(), None); /// assert_eq!(vec, vec![2, 3, 4].into()); /// ``` pub fn iter_mut(&mut self) -> IterMut<T> { let len = self.len(); IterMut { container: self, next_index: 0, next_rev_index: len - 1, } } /// Returns the number of elements in the set. /// /// This is a constant-time operation. /// /// # Examples /// /// ``` /// use rotated_vec::RotatedVec; /// /// let mut vec = RotatedVec::new(); /// assert_eq!(vec.len(), 0); /// vec.push(1); /// assert_eq!(vec.len(), 1); /// ``` pub fn len(&self) -> usize { self.data.len() } /// Returns `true` if the set contains no elements. /// /// This is a constant-time operation. /// /// # Examples /// /// ``` /// use rotated_vec::RotatedVec; /// /// let mut vec = RotatedVec::new(); /// assert!(vec.is_empty()); /// vec.push(1); /// assert!(!vec.is_empty()); /// ``` pub fn is_empty(&self) -> bool { self.data.is_empty() } /// Clears the vector, removing all values. /// /// This is a constant-time operation. /// /// # Examples /// /// ``` /// use rotated_vec::RotatedVec; /// /// let mut vec = RotatedVec::new(); /// vec.push(1); /// vec.clear(); /// assert!(vec.is_empty()); /// ``` pub fn clear(&mut self) { self.data.clear(); self.start_indexes.clear(); } /// Returns `true` if the `RotatedVec` contains an element equal to the /// given value. /// /// # Examples /// /// ``` /// use rotated_vec::RotatedVec; /// /// let mut vec = RotatedVec::new(); /// /// vec.push(0); /// vec.push(1); /// /// assert_eq!(vec.contains(&1), true); /// assert_eq!(vec.contains(&10), false); /// ``` pub fn contains(&self, x: &T) -> bool where T: PartialEq<T> { self.data.contains(x) } /// Appends an element to the back of a collection. /// /// This is a constant-time operation. /// /// # Panics /// /// Panics if the number of elements in the vector overflows a `usize`. /// /// # Examples /// /// ``` /// use rotated_vec::RotatedVec; /// /// let mut vec: RotatedVec<_> = vec![1, 2].into(); /// vec.push(3); /// assert_eq!(vec, vec![1, 2, 3].into()); /// ``` pub fn push(&mut self, value: T) { self.insert(self.len(), value); } /// Removes the last element from a vector and returns it, or [`None`] if it /// is empty. /// /// This is a constant-time operation. /// /// # Examples /// /// ``` /// use rotated_vec::RotatedVec; /// /// let mut vec: RotatedVec<_> = vec![1, 2, 3].into(); /// assert_eq!(vec.pop(), Some(3)); /// assert_eq!(vec, vec![1, 2].into()); /// ``` pub fn pop(&mut self) -> Option<T> { if self.is_empty() { None } else { Some(self.remove(self.len() - 1)) } } /// Inserts an element at position `index` within the vector. /// /// This is an `O(√n)` operation. /// /// # Panics /// /// Panics if `index > len`. /// /// # Examples /// /// /// ``` /// use rotated_vec::RotatedVec; /// /// let mut vec: RotatedVec<_> = vec![1, 2, 3].into(); /// vec.insert(1, 4); /// assert_eq!(vec, vec![1, 4, 2, 3].into()); /// vec.insert(4, 5); /// assert_eq!(vec, vec![1, 4, 2, 3, 5].into()); /// ``` pub fn insert(&mut self, index: usize, element: T) { assert!(index <= self.len()); let insert_idx = if index < self.len() { self.get_real_index(index) } else { self.len() }; // find subarray containing this insertion point let subarray_idx = Self::get_subarray_idx_from_array_idx(insert_idx); // inserted element could be in a new subarray debug_assert!(subarray_idx <= self.start_indexes.len()); // create a new subarray if necessary if subarray_idx == self.start_indexes.len() { self.start_indexes.push(0); } let subarray_offset = Self::get_array_idx_from_subarray_idx(subarray_idx); // if insertion point is in last subarray and last subarray isn't full, just insert the new element if subarray_idx == self.start_indexes.len() - 1 && !self.is_last_subarray_full() { // Since we always insert into a partially full subarray in order, // there is no need to update the pivot location. debug_assert!(self.start_indexes[subarray_idx] == 0); self.data.insert(insert_idx, element); debug_assert!(self.assert_invariants()); return; } // From now on, we can assume that the subarray we're inserting into is always full. let next_subarray_offset = Self::get_array_idx_from_subarray_idx(subarray_idx + 1); let subarray = &mut self.data[subarray_offset..next_subarray_offset]; let pivot_offset = self.start_indexes[subarray_idx]; let insert_offset = insert_idx - subarray_offset; let end_offset = if pivot_offset == 0 { subarray.len() - 1 } else { pivot_offset - 1 }; let mut prev_end_elem = subarray[end_offset]; // this logic is best understood with a diagram of a rotated array, e.g.: // // ------------------------------------------------------------------------ // | 12 | 13 | 14 | 15 | 16 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | // ------------------------------------------------------------------------ // if end_offset < pivot_offset && insert_offset >= pivot_offset { subarray.copy_within(pivot_offset..insert_offset, end_offset); subarray[insert_offset - 1] = element; self.start_indexes[subarray_idx] = end_offset; } else { subarray.copy_within(insert_offset..end_offset, insert_offset + 1); subarray[insert_offset] = element; } debug_assert!(self.assert_invariants()); let max_subarray_idx = self.start_indexes.len() - 1; let next_subarray_idx = subarray_idx + 1; let last_subarray_full = self.is_last_subarray_full(); // now loop over all remaining subarrays, setting the first (pivot) of each to the last of its predecessor for (i, pivot_offset_ref) in self.start_indexes[next_subarray_idx..].iter_mut().enumerate() { let cur_subarray_idx = next_subarray_idx + i; // if the last subarray isn't full, skip it if cur_subarray_idx == max_subarray_idx && !last_subarray_full { break; } let end_offset = if *pivot_offset_ref == 0 { cur_subarray_idx } else { *pivot_offset_ref - 1 }; let end_idx = end_offset + Self::get_array_idx_from_subarray_idx(cur_subarray_idx); let next_end_elem = self.data[end_idx]; self.data[end_idx] = prev_end_elem; *pivot_offset_ref = end_offset; prev_end_elem = next_end_elem; } // if the last subarray was full, append current last element to a new subarray, otherwise insert last element in rotated order if last_subarray_full { self.data.push(prev_end_elem); self.start_indexes.push(0); } else { let max_subarray_offset = Self::get_array_idx_from_subarray_idx(max_subarray_idx); // since `prev_end_elem` is guaranteed to be <= the pivot value, we always insert it at the pivot location self.data.insert(max_subarray_offset, prev_end_elem); } // debug_assert!(self.data[self.get_real_index(index)] == element); debug_assert!(self.assert_invariants()); } /// Removes and returns the element at position `index` within the vector. /// /// This is an `O(√n)` operation. /// /// # Panics /// /// Panics if `index` is out of bounds. /// /// # Examples /// /// ``` /// use rotated_vec::RotatedVec; /// /// let mut vec: RotatedVec<_> = vec![1, 2, 3].into(); /// assert_eq!(vec.remove(1), 2); /// assert_eq!(vec, vec![1, 3].into()); /// ``` pub fn remove(&mut self, index: usize) -> T { assert!(index < self.len()); let old_len = self.len(); let mut remove_idx = self.get_real_index(index); let element = self.data[remove_idx]; let max_subarray_idx = self.start_indexes.len() - 1; let max_subarray_offset = Self::get_array_idx_from_subarray_idx(max_subarray_idx); // find subarray containing the element to remove let subarray_idx = Self::get_subarray_idx_from_array_idx(remove_idx); debug_assert!(subarray_idx <= max_subarray_idx); let subarray_offset = Self::get_array_idx_from_subarray_idx(subarray_idx); // if we're not removing an element in the last subarray, then we end up deleting its first element, // which is always at the first offset since it's in order let mut max_subarray_remove_idx = if subarray_idx == max_subarray_idx { remove_idx } else { max_subarray_offset }; // if the last subarray was rotated, un-rotate it to maintain insert invariant if self.is_last_subarray_full() { let last_start_offset = self.start_indexes[max_subarray_idx]; // rotate left by the start offset self.data[max_subarray_offset..].rotate_left(last_start_offset); self.start_indexes[max_subarray_idx] = 0; // the remove index might change after un-rotating the last subarray if subarray_idx == max_subarray_idx { remove_idx = self.get_real_index(index); max_subarray_remove_idx = remove_idx; } } // if insertion point is not in last subarray, perform a "hard exchange" if subarray_idx < max_subarray_idx { // From now on, we can assume that the subarray we're removing from is full. let next_subarray_offset = Self::get_array_idx_from_subarray_idx(subarray_idx + 1); let subarray = &mut self.data[subarray_offset..next_subarray_offset]; let pivot_offset = self.start_indexes[subarray_idx]; let remove_offset = remove_idx - subarray_offset; let end_offset = if pivot_offset == 0 { subarray.len() - 1 } else { pivot_offset - 1 }; // this logic is best understood with a diagram of a rotated array, e.g.: // // ------------------------------------------------------------------------ // | 12 | 13 | 14 | 15 | 16 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | // ------------------------------------------------------------------------ // let mut prev_end_offset = if end_offset < pivot_offset && remove_offset >= pivot_offset { subarray.copy_within(pivot_offset..remove_offset, pivot_offset + 1); let new_pivot_offset = if pivot_offset == subarray.len() - 1 { 0 } else { pivot_offset + 1 }; self.start_indexes[subarray_idx] = new_pivot_offset; pivot_offset } else { subarray.copy_within(remove_offset + 1..=end_offset, remove_offset); end_offset }; let next_subarray_idx = min(max_subarray_idx, subarray_idx + 1); // now perform an "easy exchange" in all remaining subarrays except the last, // setting the last element of each to the first element of its successor. for (i, pivot_offset_ref) in self.start_indexes[next_subarray_idx..max_subarray_idx] .iter_mut() .enumerate() { let cur_subarray_idx = next_subarray_idx + i; let cur_subarray_offset = Self::get_array_idx_from_subarray_idx(cur_subarray_idx); let prev_end_idx = prev_end_offset + Self::get_array_idx_from_subarray_idx(cur_subarray_idx - 1); self.data[prev_end_idx] = self.data[cur_subarray_offset + *pivot_offset_ref]; prev_end_offset = *pivot_offset_ref; let new_start_offset = if *pivot_offset_ref == cur_subarray_idx { 0 } else { *pivot_offset_ref + 1 }; *pivot_offset_ref = new_start_offset; } // now we fix up the last subarray. if it was initially full, we need to un-rotate it to maintain the insert invariant. // if the removed element is in the last subarray, we just un-rotate and remove() on the vec, updating auxiliary arrays. // otherwise, we copy the first element to the last position of the previous subarray, then remove it and fix up // auxiliary arrays. let prev_end_idx = prev_end_offset + Self::get_array_idx_from_subarray_idx(max_subarray_idx - 1); // since the last subarray is always in order, its first element is always on the first offset self.data[prev_end_idx] = self.data[max_subarray_offset]; } self.data.remove(max_subarray_remove_idx); // if last subarray is now empty, trim start_indexes if max_subarray_offset == self.data.len() { self.start_indexes.pop(); } debug_assert!(self.len() == old_len - 1); debug_assert!(self.assert_invariants()); element } /// Moves all the elements of `other` into `self`, leaving `other` empty. /// /// # Panics /// /// Panics if the number of elements in the array overflows a `usize`. /// /// # Examples /// /// ``` /// use rotated_vec::RotatedVec; /// /// let mut vec: RotatedVec<_> = vec![1, 2, 3].into(); /// let mut vec2: RotatedVec<_> = vec![4, 5, 6].into(); /// vec.append(&mut vec2); /// assert_eq!(vec, vec![1, 2, 3, 4, 5, 6].into()); /// assert_eq!(vec2, vec![].into()); /// ``` pub fn append(&mut self, other: &mut Self) { // if the last subarray is partially full, un-rotate it so we can append directly if !self.is_last_subarray_full() { self.unrotate_last_subarray(); } // append data directly to backing array self.data.append(&mut other.data); // fix up start indexes let last_subarray_idx = Self::get_subarray_idx_from_array_idx(self.data.len() - 1); self.start_indexes.resize(last_subarray_idx + 1, 0); // clear all data in `other` other.clear(); } /// Sorts the vector. /// /// This sort is stable (i.e., does not reorder equal elements) and `O(n log n)` worst-case. /// /// When applicable, unstable sorting is preferred because it is generally faster than stable /// sorting and it doesn't allocate auxiliary memory. /// See [`sort_unstable`](#method.sort_unstable). /// /// # Current implementation /// /// The current algorithm is an adaptive, iterative merge sort inspired by /// [timsort](https://en.wikipedia.org/wiki/Timsort). /// It is designed to be very fast in cases where the vector is nearly sorted, or consists of /// two or more sorted sequences concatenated one after another. /// /// Also, it allocates temporary storage half the size of `self`, but for short vectors a /// non-allocating insertion sort is used instead. /// /// # Examples /// /// ``` /// use is_sorted::IsSorted; /// use rotated_vec::RotatedVec; /// /// let mut vec: RotatedVec<_> = vec![-5, 4, 1, -3, 2].into(); /// /// vec.sort(); /// assert!(IsSorted::is_sorted(&mut vec.iter())); /// ``` pub fn sort(&mut self) where T: Ord { self.data.sort(); // TODO: we really want slice.fill() here when it becomes available for idx in self.start_indexes.as_mut_slice() { *idx = 0; } } /// Sorts the vector, but may not preserve the order of equal elements. /// /// This sort is unstable (i.e., may reorder equal elements), in-place /// (i.e., does not allocate), and `O(n log n)` worst-case. /// /// # Current implementation /// /// The current algorithm is based on [pattern-defeating quicksort][pdqsort] by Orson Peters, /// which combines the fast average case of randomized quicksort with the fast worst case of /// heapsort, while achieving linear time on vectors with certain patterns. It uses some /// randomization to avoid degenerate cases, but with a fixed seed to always provide /// deterministic behavior. /// /// It is typically faster than stable sorting, except in a few special cases, e.g., when the /// vector consists of several concatenated sorted sequences. /// /// # Examples /// /// ``` /// use is_sorted::IsSorted; /// use rotated_vec::RotatedVec; /// /// let mut vec: RotatedVec<_> = vec![-5, 4, 1, -3, 2].into(); /// /// vec.sort_unstable(); /// assert!(IsSorted::is_sorted(&mut vec.iter())); /// ``` /// /// [pdqsort]: https://github.com/orlp/pdqsort pub fn sort_unstable(&mut self) where T: Ord { self.data.sort_unstable(); // TODO: we really want slice.fill() here when it becomes available for idx in self.start_indexes.as_mut_slice() { *idx = 0; } } // this returns the index in the backing array of the given logical index fn get_real_index(&self, index: usize) -> usize { debug_assert!(index < self.data.len()); let subarray_idx = Self::get_subarray_idx_from_array_idx(index); let subarray_start_idx = Self::get_array_idx_from_subarray_idx(subarray_idx); let subarray_len = if subarray_idx == self.start_indexes.len() - 1 { self.data.len() - subarray_start_idx } else { subarray_idx + 1 }; debug_assert!(index >= subarray_start_idx); let idx_offset = index - subarray_start_idx; let pivot_offset = self.start_indexes[subarray_idx]; let rotated_offset = (pivot_offset + idx_offset) % subarray_len; debug_assert!(rotated_offset < subarray_len); let real_idx = subarray_start_idx + rotated_offset; real_idx } fn integer_sum(n: usize) -> usize { // I learned this from a 10-year-old named Gauss (n * (n + 1)) / 2 } fn integer_sum_inverse(n: usize) -> usize { // y = (x * (x + 1)) / 2 // x = (sqrt(8 * y + 1) - 1) / 2 ((f64::from((n * 8 + 1) as u32).sqrt() as usize) - 1) / 2 } fn get_subarray_idx_from_array_idx(idx: usize) -> usize { if idx == 0 { 0 } else { Self::integer_sum_inverse(idx) } } fn get_array_idx_from_subarray_idx(idx: usize) -> usize { if idx == 0 { 0 } else { Self::integer_sum(idx) } } fn is_last_subarray_full(&self) -> bool { self.data.len() == Self::get_array_idx_from_subarray_idx(self.start_indexes.len()) } fn unrotate_last_subarray(&mut self) { let last_subarray_idx = Self::get_subarray_idx_from_array_idx(self.len() - 1); let last_subarray_start_idx = Self::get_array_idx_from_subarray_idx(last_subarray_idx); let last_subarray_len = if last_subarray_idx == self.start_indexes.len() - 1 { self.len() - last_subarray_start_idx } else { last_subarray_idx + 1 }; let last_subarray_end_idx = last_subarray_start_idx + last_subarray_len; let last_subarray = &mut self.data[last_subarray_start_idx..last_subarray_end_idx]; // un-rotate subarray in-place let pivot_offset = self.start_indexes[last_subarray_idx]; last_subarray.rotate_left(pivot_offset); self.start_indexes[last_subarray_idx] = 0; } #[inline(always)] fn assert_invariants(&self) -> bool { // assert offset array has proper length let expected_start_indexes_len = if self.is_empty() { 0 } else { Self::get_subarray_idx_from_array_idx(self.len() - 1) + 1 }; assert_eq!(self.start_indexes.len(), expected_start_indexes_len); // assert index of each subarray's first element lies within the subarray assert!(self .start_indexes .iter() .enumerate() .all(|(idx, &offset)| offset <= idx)); true } // given data array, initialize offset array fn init(&mut self) { debug_assert!(self.start_indexes.is_empty()); if !self.data.is_empty() { let last_subarray_idx = Self::get_subarray_idx_from_array_idx(self.data.len() - 1); self.start_indexes = vec![0; last_subarray_idx + 1]; } } } impl<T> PartialEq for RotatedVec<T> where T: Copy + Default + Debug + PartialEq, { fn eq(&self, other: &Self) -> bool { if self.len() != other.len() { return false; } for i in 0..self.len() { if self.get(i).unwrap() != other.get(i).unwrap() { return false; } } true } } impl<T> Eq for RotatedVec<T> where T: Copy + Default + Debug + PartialEq {} impl<T> PartialOrd for RotatedVec<T> where T: Copy + Default + Debug + PartialOrd { fn partial_cmp(&self, other: &RotatedVec<T>) -> Option<Ordering> { self.iter().partial_cmp(other.iter()) } } impl<T> Ord for RotatedVec<T> where T: Copy + Default + Debug + Ord { fn cmp(&self, other: &RotatedVec<T>) -> Ordering { self.iter().cmp(other.iter()) } } impl<T> Hash for RotatedVec<T> where T: Copy + Default + Debug + PartialEq + Hash { fn hash<H: Hasher>(&self, state: &mut H) { for i in 0..self.len() { self.get(i).hash(state); } } } impl<T> Index<usize> for RotatedVec<T> where T: Copy + Default + Debug, { type Output = T; #[inline] fn index(&self, index: usize) -> &T { self.get(index).expect("Out of bounds access") } } impl<T> IndexMut<usize> for RotatedVec<T> where T: Copy + Default + Debug, { #[inline] fn index_mut(&mut self, index: usize) -> &mut T { self.get_mut(index).expect("Out of bounds access") } } impl<T> Extend<T> for RotatedVec<T> where T: Copy + Default + Debug, { fn extend<I>(&mut self, iter: I) where I: IntoIterator<Item = T>, { // if the last subarray is partially full, un-rotate it so we can append directly if !self.is_last_subarray_full() { self.unrotate_last_subarray(); } // append data directly to backing array self.data.extend(iter); // fix up start indexes let last_subarray_idx = Self::get_subarray_idx_from_array_idx(self.data.len() - 1); self.start_indexes.resize(last_subarray_idx + 1, 0); } } impl<'a, T> Iterator for Iter<'a, T> where T: Copy + Default + Debug, { type Item = &'a T; fn next(&mut self) -> Option<Self::Item> { if self.len() == 0 || self.next_index > self.next_rev_index { None } else { let current = self.container.get(self.next_index); self.next_index += 1; debug_assert!(self.assert_invariants()); current } } fn nth(&mut self, n: usize) -> Option<Self::Item> { self.next_index = min(self.next_index + n, self.len()); let ret = if self.len() == 0 || self.next_index > self.next_rev_index { None } else { let nth = self.container.get(self.next_index); self.next_index += 1; nth }; debug_assert!(self.assert_invariants()); ret } fn count(self) -> usize { self.len() - self.next_index } fn last(self) -> Option<Self::Item> { if self.len() == 0 { None } else { self.container.get(self.len() - 1) } } fn max(self) -> Option<Self::Item> { if self.len() == 0 { None } else { self.container.get(self.len() - 1) } } fn min(self) -> Option<Self::Item> { self.container.get(0) } fn size_hint(&self) -> (usize, Option<usize>) { let remaining_count = self.len() - self.next_index; (remaining_count, Some(remaining_count)) } } impl<'a, T> DoubleEndedIterator for Iter<'a, T> where T: Copy + Default + Debug, { fn next_back(&mut self) -> Option<Self::Item> { if self.len() == 0 || self.next_rev_index < self.next_index { None } else { let current = self.container.get(self.next_rev_index); // We can't decrement next_rev_index past 0, so we cheat and move next_index // ahead instead. That works since next() must return None once next_rev_index // has crossed next_index. if self.next_rev_index == 0 { self.next_index += 1; } else { self.next_rev_index -= 1; } debug_assert!(self.assert_invariants()); current } } fn nth_back(&mut self, n: usize) -> Option<Self::Item> { self.next_rev_index = self.next_rev_index.saturating_sub(n); let ret = if self.len() == 0 || self.next_rev_index < self.next_index { None } else { let nth = self.container.get(self.next_rev_index); // We can't decrement next_rev_index past 0, so we cheat and move next_index // ahead instead. That works since next() must return None once next_rev_index // has crossed next_index. if self.next_rev_index == 0 { self.next_index += 1; } else { self.next_rev_index -= 1; } nth }; debug_assert!(self.assert_invariants()); ret } } impl<T> ExactSizeIterator for Iter<'_, T> where T: Copy + Default + Debug, { fn len(&self) -> usize { self.container.len() } } impl<T> FusedIterator for Iter<'_, T> where T: Copy + Default + Debug {} impl<'a, T> Iterator for IterMut<'a, T> where T: Copy + Default + Debug, { type Item = &'a mut T; // unsafe code required, see: // https://www.reddit.com/r/rust/comments/6ffrbs/implementing_a_safe_mutable_iterator/ // https://stackoverflow.com/questions/25730586/how-can-i-create-my-own-data-structure-with-an-iterator-that-returns-mutable-ref // https://stackoverflow.com/questions/27118398/simple-as-possible-example-of-returning-a-mutable-reference-from-your-own-iterat fn next(&mut self) -> Option<Self::Item> { let ret = if self.len() == 0 || self.next_index > self.next_rev_index { None } else { let current = self.container.get_mut(self.next_index); self.next_index += 1; // see MutItems example at https://docs.rs/strided/0.2.9/src/strided/base.rs.html // per above links, rustc cannot understand that we never return two mutable references to the same object, // so we have to use unsafe code to coerce the return value to the desired lifetime unsafe { mem::transmute(current) } }; debug_assert!(self.assert_invariants()); ret } fn nth(&mut self, n: usize) -> Option<Self::Item> { self.next_index = min(self.next_index + n, self.len()); let ret = if self.len() == 0 || self.next_index > self.next_rev_index { None } else { let nth = self.container.get_mut(self.next_index); self.next_index += 1; // per above links, rustc cannot understand that we never return two mutable references to the same object, // so we have to use unsafe code to coerce the return value to the desired lifetime unsafe { mem::transmute(nth) } }; debug_assert!(self.assert_invariants()); ret } fn count(self) -> usize { self.len() - self.next_index } fn last(self) -> Option<Self::Item> { if self.len() == 0 { None } else { self.container.get_mut(self.len() - 1) } } fn size_hint(&self) -> (usize, Option<usize>) { let remaining_count = self.len() - self.next_index; (remaining_count, Some(remaining_count)) } } impl<'a, T> DoubleEndedIterator for IterMut<'a, T> where T: Copy + Default + Debug, { fn next_back(&mut self) -> Option<Self::Item> { if self.len() == 0 || self.next_rev_index < self.next_index { None } else { let current = self.container.get(self.next_rev_index); // We can't decrement next_rev_index past 0, so we cheat and move next_index // ahead instead. That works since next() must return None once next_rev_index // has crossed next_index. if self.next_rev_index == 0 { self.next_index += 1; } else { self.next_rev_index -= 1; } debug_assert!(self.assert_invariants()); // per above links, rustc cannot understand that we never return two mutable references to the same object, // so we have to use unsafe code to coerce the return value to the desired lifetime unsafe { mem::transmute(current) } } } fn nth_back(&mut self, n: usize) -> Option<Self::Item> { self.next_rev_index = self.next_rev_index.saturating_sub(n); let ret = if self.len() == 0 || self.next_rev_index < self.next_index { None } else { let nth = self.container.get(self.next_rev_index); // We can't decrement next_rev_index past 0, so we cheat and move next_index // ahead instead. That works since next() must return None once next_rev_index // has crossed next_index. if self.next_rev_index == 0 { self.next_index += 1; } else { self.next_rev_index -= 1; } // per above links, rustc cannot understand that we never return two mutable references to the same object, // so we have to use unsafe code to coerce the return value to the desired lifetime unsafe { mem::transmute(nth) } }; debug_assert!(self.assert_invariants()); ret } } impl<T> ExactSizeIterator for IterMut<'_, T> where T: Copy + Default + Debug, { fn len(&self) -> usize { self.container.len() } } impl<T> FusedIterator for IterMut<'_, T> where T: Copy + Default + Debug {} impl<'a, T> IntoIterator for &'a RotatedVec<T> where T: Copy + Default + Debug, { type Item = &'a T; type IntoIter = Iter<'a, T>; fn into_iter(self) -> Self::IntoIter { self.iter() } } impl<'a, T> IntoIterator for &'a mut RotatedVec<T> where T: Copy + Default + Debug, { type Item = &'a mut T; type IntoIter = IterMut<'a, T>; fn into_iter(self) -> Self::IntoIter { self.iter_mut() } } impl<T> IntoIterator for RotatedVec<T> where T: Copy + Default + Debug, { type Item = T; type IntoIter = IntoIter<T>; fn into_iter(self) -> Self::IntoIter { IntoIter { vec: self.into(), next_index: 0, } } } impl<'a, T> Iterator for IntoIter<T> where T: Copy + Default + Debug, { type Item = T; fn next(&mut self) -> Option<Self::Item> { if self.next_index == self.vec.len() { None } else { let current = self.vec[self.next_index]; self.next_index += 1; debug_assert!(self.next_index <= self.vec.len()); Some(current) } } } impl<'a, T> From<&'a [T]> for RotatedVec<T> where T: Copy + Default + Debug, { fn from(slice: &'a [T]) -> Self { let mut this = RotatedVec { data: slice.to_vec(), start_indexes: Vec::new(), }; this.init(); this } } impl<T> From<Vec<T>> for RotatedVec<T> where T: Copy + Default + Debug, { fn from(vec: Vec<T>) -> Self { let mut this = RotatedVec { data: vec, start_indexes: Vec::new(), }; this.init(); this } } impl<T> Into<Vec<T>> for RotatedVec<T> where T: Copy + Default + Debug, { fn into(mut self) -> Vec<T> { // un-rotate the data array in-place and steal it from self for (i, &pivot_offset) in self.start_indexes.iter().enumerate() { let subarray_start_idx = Self::get_array_idx_from_subarray_idx(i); let subarray_len = if i == self.start_indexes.len() - 1 { self.data.len() - subarray_start_idx } else { i + 1 }; let subarray_end_idx = subarray_start_idx + subarray_len; let subarray = &mut self.data[subarray_start_idx..subarray_end_idx]; // un-rotate subarray in-place subarray.rotate_left(pivot_offset); } // steal data array self.data } } impl<T> FromIterator<T> for RotatedVec<T> where T: Copy + Default + Debug, { fn from_iter<I: IntoIterator<Item = T>>(iter: I) -> Self { let mut this = RotatedVec { data: Vec::from_iter(iter.into_iter()), start_indexes: Vec::new(), }; this.init(); this } } impl<T> Default for RotatedVec<T> where T: Copy + Default + Debug, { #[inline] fn default() -> RotatedVec<T> { RotatedVec::new() } }