Sort array by increasing frequency

Array Hash Table Sorting

80.7% acceptance

Feb 25, 2026

3702

179

Given an array of integers nums, sort the array in increasing order based on the frequency of the values. If multiple values have the same frequency, sort them in decreasing order. Return the sorted array.

Solution

Rust

Time O(n log n)

Space O(n)

LeetCode

solution.rs

use std::collections::HashMap;

impl Solution {
  pub fn frequency_sort(mut nums: Vec<i32>) -> Vec<i32> {
    let mut freq: HashMap<i32, i32> = HashMap::new();
    for &n in &nums { *freq.entry(n).or_insert(0) += 1; }
    nums.sort_by(|a, b| {
      let fa = freq[a];
      let fb = freq[b];
      fa.cmp(&fb).then(b.cmp(a))
    });
    nums
  }
}