treez 1.6.0

A collection of useful data structures.
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144

//! monotonic queue
//! items are ordered such that all elements are non-decreasing
//! compared using cmp::Ordering::Less (eg: e_i >= e_j, for all i > j)

use std::cmp::Ordering;
use std::collections::VecDeque;

#[cfg(test)]
extern crate rand;
#[cfg(test)]
use self::rand::{thread_rng, Rng};

pub struct QueueMonotone<T>
where
    T: Ord + Clone,
{
    /// (value of element, number of smaller elements between current element and previous element)
    data: VecDeque<(T, usize)>,

    /// logical length of data
    length: usize,

    /// this sets a moving window for data storage and computation
    auto_length: Option<usize>,
}

impl<T> QueueMonotone<T>
where
    T: Ord + Clone,
{
    fn new() -> QueueMonotone<T> {
        QueueMonotone {
            data: VecDeque::new(),
            length: 0,
            auto_length: None,
        }
    }
    /// item is pushed in the back and compressed for items that are < current item
    fn push(&mut self, i: T) {
        let mut num_elements = 0;

        let mut count = 0;

        for item in self.data.iter().rev() {
            if item.0.cmp(&i) == Ordering::Less {
                num_elements += item.1 + 1;
                count += 1;
            } else {
                break;
            }
        }

        self.data.truncate(self.data.len() - count);

        self.data.push_back((i, num_elements));
        self.length += 1;

        match self.auto_length {
            Some(x) if self.length > x => {
                self.pop();
            }
            _ => {}
        }
    }
    /// item is popped from the front
    fn pop(&mut self) {
        match self.data.front_mut() {
            Some(x) => {
                if x.1 > 0 {
                    x.1 -= 1;
                } else {
                    self.data.pop_front();
                }
                self.length -= 1;
            }
            _ => {}
        }
    }
    /// query max in queue
    fn max(&self) -> Option<&T> {
        match self.data.front() {
            Some(x) => Some(&x.0),
            _ => None,
        }
    }
    fn len(&self) -> usize {
        self.length
    }
    fn set_auto_len(&mut self, l: usize) {
        self.auto_length = Some(l);
    }
}

#[test]
fn test0() {
    let mut q: QueueMonotone<i32> = QueueMonotone::new();
    for i in 0..10 {
        q.push(i);
        assert_eq!(q.max().expect("max"), &i);
        assert_eq!(q.len(), i as usize + 1);
    }
}
#[test]
fn test1() {
    let mut q: QueueMonotone<i32> = QueueMonotone::new();
    for i in 0..10 {
        q.push(i);
    }
    for i in 0..10 {
        q.pop();
        if i != 9 {
            assert_eq!(q.max().expect("max"), &9);
        } else {
            assert_eq!(q.max().is_none(), true);
        }
        assert_eq!(q.len(), 10 - i as usize - 1);
    }
    q.pop();
    assert_eq!(q.max().is_none(), true);
}
#[test]
fn test2() {
    let mut q: QueueMonotone<i32> = QueueMonotone::new();

    const window: usize = 20;

    q.set_auto_len(window);

    let mut rng = rand::thread_rng();

    let arr: Vec<i32> = (0..100).map(|x| rng.gen_range(-1000, 1000)).collect();

    for (i, v) in arr.iter().enumerate() {
        q.push(*v);

        assert!(q.len() <= window);

        let bound_left = std::cmp::max((i + 1).saturating_sub(window), 0);

        let m = *q.max().expect("max");

        assert_eq!(m, *arr[bound_left..=i].iter().max().unwrap());
    }
}