LeetCode 1089. Duplicate Zeros (

Given a fixed length array arr of integers, duplicate each occurrence of zero, shifting the remaining elements to the right.

Note that elements beyond the length of the original array are not written.

Do the above modifications to the input array in place, do not return anything from your function.

Example 1:
Input: [1,0,2,3,0,4,5,0]
Output: null
Explanation: After calling your function, the input array is modified to: [1,0,0,2,3,0,0,4]

Example 2:
Input: [1,2,3]
Output: null
Explanation: After calling your function, the input array is modified to: [1,2,3]

Note:
1 <= arr.length <= 10000
0 <= arr[i] <= 9

Solution:

class Solution:
    def duplicateZeros(self, arr: List[int]) -> None:
        """
        Do not return anything, modify arr in-place instead.
        """
        i = 0
        n = len(arr)

        while i < n:
            if arr[i] == 0:
                arr.pop()
                arr.insert(i,0)
                i += 1
            i += 1

Explanation:
We scan the arr from left to right, if the i-th element is equal to 0, we pop the last arr to make a position for replicating a new 0. Just keep in mind that i has to be less than n, because we don't need to do anything for the last element even though it is 0. Otherwise, we will see an index error(out of range), because we need to delete the last element and original index is gone.