[LeetCode] Replace Elements with Greatest Element on Right Side

🔍  문제

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.

Input: arr = [17,18,5,4,6,1]
Output: [18,6,6,6,1,-1]
Explanation: 
- index 0 --> the greatest element to the right of index 0 is index 1 (18).
- index 1 --> the greatest element to the right of index 1 is index 4 (6).
- index 2 --> the greatest element to the right of index 2 is index 4 (6).
- index 3 --> the greatest element to the right of index 3 is index 4 (6).
- index 4 --> the greatest element to the right of index 4 is index 5 (1).
- index 5 --> there are no elements to the right of index 5, so we put -1.

 

🖥  실행

1) Answer

class Solution:
    def replaceElements(self, arr: List[int])
        for i, n in enumerate(arr):
            if i == len(arr)-1:
                arr[i] = -1
            else:    
                arr[i] = max(arr[i+1:])
        return arr

 

2) Better Solution

class Solution:
def replaceElements(self, arr: List[int])
        m = -1
        i = len(arr) -1 
        while i >= 0:
            temp = arr[i]
            arr[i] = m
            if temp > m:
                m = temp
            i-= 1
        return arr