1636. Sort Array by Increasing Frequency

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.

 

Example 1:

Input: nums = [1,1,2,2,2,3]
Output: [3,1,1,2,2,2]
Explanation: '3' has a frequency of 1, '1' has a frequency of 2, and '2' has a frequency of 3.

Example 2:

Input: nums = [2,3,1,3,2]
Output: [1,3,3,2,2]
Explanation: '2' and '3' both have a frequency of 2, so they are sorted in decreasing order.

Example 3:

Input: nums = [-1,1,-6,4,5,-6,1,4,1]
Output: [5,-1,4,4,-6,-6,1,1,1]

 

Constraints:

  • 1 <= nums.length <= 100
  • -100 <= nums[i] <= 100

Rust Solution

struct Solution;
use std::cmp::Reverse;
use std::collections::HashMap;

impl Solution {
    fn frequency_sort(mut nums: Vec<i32>) -> Vec<i32> {
        let n = nums.len();
        let mut count: HashMap<i32, usize> = HashMap::new();
        for i in 0..n {
            *count.entry(nums[i]).or_default() += 1;
        }
        nums.sort_by_key(|&x| (count[&x], Reverse(x)));
        nums
    }
}

#[test]
fn test() {
    let nums = vec![1, 1, 2, 2, 2, 3];
    let res = vec![3, 1, 1, 2, 2, 2];
    assert_eq!(Solution::frequency_sort(nums), res);
    let nums = vec![2, 3, 1, 3, 2];
    let res = vec![1, 3, 3, 2, 2];
    assert_eq!(Solution::frequency_sort(nums), res);
    let nums = vec![-1, 1, -6, 4, 5, -6, 1, 4, 1];
    let res = vec![5, -1, 4, 4, -6, -6, 1, 1, 1];
    assert_eq!(Solution::frequency_sort(nums), res);
}

Having problems with this solution? Click here to submit an issue on github.