Array篇easy难度之求某一个索引后面的最大元素

关键字

倒序遍历

题目描述

https://leetcode.com/problems/replace-elements-with-greatest-element-on-right-side/

Given an array arr, replace every element in that array with the greatest element among the elements to its right, and replace the last element with -1.

After doing so, return the array.

 

Example 1:

Input: arr = [17,18,5,4,6,1]
Output: [18,6,6,6,1,-1]
 

Constraints:

1 <= arr.length <= 10^4
1 <= arr[i] <= 10^5

博主提交的代码

一坨屎就是

public int[] replaceElements(int[] arr) {
        int[] result = new int[arr.length];
        for(int i = 0; i < arr.length ;i++){
            int now = arr[i];
            if( i + 1 < arr.length ){
                int max = arr[i + 1];
                for(int j = i +1; j< arr.length; j++){
                    if( max< arr[j]){
                        max = arr[j];
                    }
                }
                result[i] = max;
                
            } else{
                result[i] = -1;
            }

        }
        return result;
    }

他人优秀的代码

https://leetcode.com/problems/replace-elements-with-greatest-element-on-right-side/discuss/463249/JavaC%2B%2BPython-Straight-Forward
这个人是真的大神
简洁版

 public int[] replaceElements(int[] A) {
        for (int i = A.length - 1, mx = -1; i >= 0; --i)
            mx = Math.max(A[i], A[i] = mx);
        return A;
    }

扩展版

public int[] replaceElements2(int[] A) {
        int mx = -1, n = A.length, a;
        for (int i = n - 1; i >= 0; --i) {
            a = A[i];
            A[i] = mx;
            mx = Math.max(mx, a);
        }
        return A;
    }