【leetcode】1299. Replace Elements with Greatest Element on Right Side

题目如下：

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

解题思路：从右往左遍历arr，同时记录出现的最大值即可。

代码如下：

class Solution(object):
    def replaceElements(self, arr):
        """
        :type arr: List[int]
        :rtype: List[int]
        """
        res = [-1]
        max_val = arr[-1]
        for i in range(len(arr)-2,-1,-1):
            res.insert(0,max_val)
            max_val = max(arr[i], max_val)
        return res