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  • 1331. Rank Transform of an Array

    package LeetCode_1331
    
    import java.util.*
    import kotlin.collections.HashMap
    
    /**
     * 1331. Rank Transform of an Array
     * https://leetcode.com/problems/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.
     * */
    class Solution {
        /*
        * solution: Array copy + HashMap, Time:O(nlogn), Space:O(n)
        * */
        fun arrayRankTransform(arr: IntArray): IntArray {
            val array = Arrays.copyOf(arr, arr.size)
            array.sort()
            //key: num, value: the index of this num in sorted array
            val map = HashMap<Int, Int>()
            for (item in array) {
                //avoid replace index if same num
                if (!map.contains(item)) {
                    map.put(item, map.size + 1)
                }
            }
            for (i in array.indices) {
                //update result by index
                array[i] = map.get(arr[i])!!
            }
            return array
        }
    }
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  • 原文地址:https://www.cnblogs.com/johnnyzhao/p/13944787.html
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