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by Sumit Chourasia | Nov 03, 2020 | Category :coding | Tags : algorithm array data-structure leetcode medium

Sort Array by Increasing Frequency - Array - Medium - LeetCode

Sort Array by Increasing Frequency - Array - Medium - LeetCode

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

public class Solution {
    public int[] FrequencySort(int[] nums) {
        var map = new Dictionary<int,int>();
        var res = new int[nums.Length];
        for(int i=0;i<nums.Length;i++){            
            if(map.ContainsKey(nums[i])){
                map[nums[i]]++;            
            }
            else{
                map.Add(nums[i],1);
            }
        }
        
        map = map.OrderBy(x=>x.Value).ThenByDescending(x=>x.Key).ToDictionary(x=> x.Key, x=>x.Value);
        int index=0;
        foreach(var item in map){            
            for(int i=0;i<item.Value;i++){
                res[index]=item.Key;
                index++;
            }
        }
        
        return res;
    }
}

Time Complexity: O(nlogn)

Space Complexity: O(n)

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