leetcode_rust/
top_k_frequent_elements.rs

1#![allow(dead_code)]
2
3pub fn top_k_frequent(nums: Vec<i32>, k: i32) -> Vec<i32> {
4    use std::collections::BinaryHeap;
5    use std::collections::HashMap;
6    let mut map = HashMap::new();
7    for num in nums {
8        match map.get_mut(&num) {
9            Some(v) => {
10                *v += 1;
11            }
12            None => {
13                map.insert(num, 1);
14            }
15        }
16    }
17    let mut heap = map
18        .into_iter()
19        .map(|(k, v)| (v, k))
20        .collect::<BinaryHeap<_>>();
21
22    let mut res = vec![];
23    for _ in 0..k {
24        heap.pop().map(|(_k, v)| res.push(v));
25    }
26
27    res
28}
29
30#[cfg(test)]
31mod tests {
32    use super::*;
33
34    #[test]
35    fn test1() {
36        let nums = vec![1, 1, 1, 2, 2, 3];
37        let k = 2;
38        assert_eq!(top_k_frequent(nums, k), vec![1, 2]);
39    }
40}