_1331.java

package com.fishercoder.solutions;

import java.util.HashMap;
import java.util.Map;
import java.util.TreeSet;

/**
 * 1331. 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:
 * Rank is an integer starting from 1.
 * The larger the element, the larger the rank. If two elements are equal, their rank must be the same.
 * Rank should be as small as possible.
 *
 * 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.
 *
 * Example 3:
 * Input: arr = [37,12,28,9,100,56,80,5,12]
 * Output: [5,3,4,2,8,6,7,1,3]
 *
 * Constraints:
 * 0 <= arr.length <= 105
 * -109 <= arr[i] <= 109
 * */
public class _1331 {
    public static class Solution1 {
        public int[] arrayRankTransform(int[] arr) {
            TreeSet<Integer> set = new TreeSet<>();
            for (int i : arr) {
                set.add(i);
            }
            Map<Integer, Integer> map = new HashMap<>();
            int rank = 1;
            for (int num : set) {
                map.put(num, rank++);
            }
            int[] ranks = new int[arr.length];
            for (int i = 0; i < arr.length; i++) {
                ranks[i] = map.get(arr[i]);
            }
            return ranks;
        }
    }
}