# 1089. Duplicate Zeros

## Description

Given a fixed-length integer array arr, 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 and do not return anything.

Example 1:

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


Example 2:

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


Constraints:

• 1 <= arr.length <= 104
• 0 <= arr[i] <= 9

## Solutions

• class Solution {
public void duplicateZeros(int[] arr) {
int n = arr.length;
int i = -1, k = 0;
while (k < n) {
++i;
k += arr[i] > 0 ? 1 : 2;
}
int j = n - 1;
if (k == n + 1) {
arr[j--] = 0;
--i;
}
while (j >= 0) {
arr[j] = arr[i];
if (arr[i] == 0) {
arr[--j] = arr[i];
}
--i;
--j;
}
}
}

• class Solution {
public:
void duplicateZeros(vector<int>& arr) {
int n = arr.size();
int i = -1, k = 0;
while (k < n) {
++i;
k += arr[i] ? 1 : 2;
}
int j = n - 1;
if (k == n + 1) {
arr[j--] = 0;
--i;
}
while (~j) {
arr[j] = arr[i];
if (arr[i] == 0) arr[--j] = arr[i];
--i;
--j;
}
}
};

• class Solution:
def duplicateZeros(self, arr: List[int]) -> None:
"""
Do not return anything, modify arr in-place instead.
"""
n = len(arr)
i, k = -1, 0
while k < n:
i += 1
k += 1 if arr[i] else 2
j = n - 1
if k == n + 1:
arr[j] = 0
i, j = i - 1, j - 1
while ~j:
if arr[i] == 0:
arr[j] = arr[j - 1] = arr[i]
j -= 1
else:
arr[j] = arr[i]
i, j = i - 1, j - 1


• func duplicateZeros(arr []int) {
n := len(arr)
i, k := -1, 0
for k < n {
i, k = i+1, k+1
if arr[i] == 0 {
k++
}
}
j := n - 1
if k == n+1 {
arr[j] = 0
i, j = i-1, j-1
}
for j >= 0 {
arr[j] = arr[i]
if arr[i] == 0 {
j--
arr[j] = arr[i]
}
i, j = i-1, j-1
}
}

• impl Solution {
pub fn duplicate_zeros(arr: &mut Vec<i32>) {
let n = arr.len();
let mut i = 0;
let mut j = 0;
while j < n {
if arr[i] == 0 {
j += 1;
}
j += 1;
i += 1;
}
while i > 0 {
if arr[i - 1] == 0 {
if j <= n {
arr[j - 1] = arr[i - 1];
}
j -= 1;
}
arr[j - 1] = arr[i - 1];
i -= 1;
j -= 1;
}
}
}