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use std::collections::HashSet;
pub struct DisjointSet {
elements: Vec<i32>,
}
impl DisjointSet {
pub fn new(size: usize) -> Self {
Self {
elements: vec![-1; size],
}
}
pub fn find(&mut self, index: usize) -> usize {
let mut root_index = index;
loop {
let value = self.elements[root_index];
if value < 0 {
break;
} else {
root_index = value as usize;
}
}
let mut new_index = index;
loop {
let value = self.elements[new_index];
if value < 0 {
break;
} else {
self.elements[new_index] = root_index as i32;
new_index = value as usize;
}
}
root_index
}
pub fn join(&mut self, i: usize, j: usize) {
let root1 = self.find(i);
let root2 = self.find(j);
if root1 == root2 {
return;
}
let r1 = self.elements[root1];
let r2 = self.elements[root2];
if r1 < r2 {
self.elements[root1] += r2;
self.elements[root2] = root1 as i32;
} else {
self.elements[root2] += r1;
self.elements[root1] = root2 as i32;
}
}
pub fn size(&mut self, i: usize) -> usize {
let root = self.find(i);
-self.elements[root] as usize
}
pub fn num_groups(&mut self) -> usize {
let mut set = HashSet::new();
for i in 0..self.elements.len() {
set.insert(self.find(i));
}
set.len()
}
}
#[test]
fn test_disjoint_set() {
let mut set = DisjointSet::new(10);
assert_eq!(1, set.size(0));
assert_eq!(10, set.num_groups());
set.join(0, 1);
assert_eq!(2, set.size(0));
assert_eq!(2, set.size(1));
assert_eq!(9, set.num_groups());
set.join(2, 3);
assert_eq!(2, set.size(0));
assert_eq!(2, set.size(3));
assert_eq!(8, set.num_groups());
set.join(1, 3);
assert_eq!(4, set.size(0));
assert_eq!(4, set.size(3));
assert_eq!(7, set.num_groups());
}