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SortArrayIncreasingFrequency.java
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SortArrayIncreasingFrequency.java
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package Leetcode;
import java.util.HashMap;
import java.util.Map;
import java.util.PriorityQueue;
/**
* @author kalpak
*
* 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 SortArrayIncreasingFrequency {
public static int[] frequencySort(int[] nums) {
int[] result = new int[nums.length];
int idx = 0;
Map<Integer, Integer> map = new HashMap<>();
PriorityQueue<Integer> minHeap = new PriorityQueue<>((a, b) -> (map.get(a) == map.get(b)) ? b - a : map.get(a) - map.get(b));
for(int i : nums) {
map.put(i, map.getOrDefault(i, 0) + 1);
}
for(int key : map.keySet())
minHeap.offer(key);
while(!minHeap.isEmpty()) {
int temp = minHeap.poll();
for(int i = map.get(temp); i > 0; i--)
result[idx++] = temp;
}
return result;
}
public static void printArray(int[] nums) {
for(int i : nums)
System.out.print(i + " ");
System.out.println();
}
public static void main(String[] args) {
int[] arr = new int[]{1,1,2,2,2,3};
printArray(frequencySort(arr));
arr = new int[]{-1,1,-6,4,5,-6,1,4,1};
printArray(frequencySort(arr));
}
}