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LeetCode – Arrays – Rank Transform of an Array

Given an array of integers arr, replace each element with its rank.

The rank represents how large the element is. The rank has the following rules:

Example 1:

Input: arr = [40,10,20,30]
Output: [4,1,2,3]
Explanation: 40 is the largest element. 10 is the smallest. 20 is the second smallest. 30 is the third smallest.

Example 2:

Input: arr = [100,100,100]
Output: [1,1,1]
Explanation: Same elements share the same rank.
class Solution {
    public int[] arrayRankTransform(int[] arr) {
        int[] temp = Arrays.copyOf(arr, arr.length);
        Arrays.sort(temp);
        Map<Integer,Integer> rankMap = new HashMap<Integer,Integer>();
        int rank = 1;
        for(int i:temp){
            if(!rankMap.containsKey(i)) rankMap.put(i,rank++);
        }
        int[] result = new int[arr.length];
        for(int i=0;i<arr.length;i++){
            result[i] = rankMap.get(arr[i]);
        }
        return result;
    }
}
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