# 2022-06-17

## [1089. Duplicate Zeros](https://leetcode.com/problems/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 <= 10^4`
* `0 <= arr[i] <= 9`

### Solution

#### Approach #0

```go
func duplicateZeros(arr []int) {
    n := len(arr)
    i, top := -1, 0
    for top < n {
        i++
        if arr[i] == 0 {
            top += 2
        } else {
            top++
        }
    }
    j := n - 1
    if top == n+1 {
        arr[j] = 0
        j--
        i--
    }
    for j > 0 {
        arr[j] = arr[i]
        j--
        if arr[i] == 0 {
            arr[j] = arr[i]
            j--
        }
        i--
    }
}
```