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

class Solution {
    public int[] replaceElements(int[] arr) {
        int n = arr.length;
        int m = arr[n - 1];
        int[] res = new int[n];
        
        for(int i = n - 1; i >= 1; i--){
            m = Math.max(arr[i], m);
            res[i - 1] = m;
        }
        res[n - 1] = -1;
        return res;
    }
}

从右到左记录每一个max