Leetcode: Duplicate Zeros

Duplicate Zeros

Similar Problems:

• CheatSheet: Leetcode For Code Interview
• CheatSheet: Common Code Problems & Follow-ups
• Tag: #twopointer, #array, #inspiring, #findduplicates

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. 1 <= arr.length <= 10000
2. 0 <= arr[i] <= 9

Github: code.dennyzhang.com

Credits To: leetcode.com

Leave me comments, if you have better ways to solve.

• Solution:

// https://code.dennyzhang.com/duplicate-zeros
// Basic Ideas: two pointer
//   Find how many cells can be shifted
//   From right to next, do the move
// Complexity: Time O(n), Space O(1)
func duplicateZeros(arr []int)  {
    count := 0
    for _, v := range arr {
        if v == 0 {
            count++
        }
    }
    i, j := len(arr)-1, len(arr)+count-1
    for ; i>=0 && j>=0; i, j = i-1, j-1 {
        if arr[i] != 0 {
            if j<len(arr) {
                arr[j] = arr[i]
            }
        } else {
            if j<len(arr) {
                arr[j] = 0
            }
            j--
            if j<len(arr) {
                arr[j] = 0
            }
        }
    }
}