1089. Duplicate Zeros

Python

class Solution:
    def duplicateZeros(self, arr: List[int]) -> None:
        """
        Do not return anything, modify arr in-place instead.
        """
        length = len(arr)
        for i in range(0, length):
            if arr[i] == 0:
                for j in range(length-1, i+1, -1):
                    arr[j] = arr[j-1]
                if i+1 < length:
                    arr[i+1] = '-'
        for i in range(0, length):
            if arr[i] == '-':
                arr[i] = 0