# 283. Move Zeroes

- Difficulty: Easy.

- Related Topics: Array, Two Pointers.

- Similar Questions: Remove Element.

## Problem

Given an array ```nums```, write a function to move all ```0```'s to the end of it while maintaining the relative order of the non-zero elements.

**Example:**

```

Input: [0,1,0,3,12]

Output: [1,3,12,0,0]

```

**Note**:

- You must do this **in-place** without making a copy of the array.

- Minimize the total number of operations.

## Solution

```javascript

/**

* @param {number[]} nums

* @return {void} Do not return anything, modify nums in-place instead.

*/

var moveZeroes = function(nums) {

var len = nums.length;

var lastZeroIndex = -1;

for (var i = 0; i < len; i++) {

if (nums[i] === 0 && lastZeroIndex === -1) {

lastZeroIndex = i;

} else if (nums[i] !== 0 && lastZeroIndex !== -1) {

swap(nums, i, lastZeroIndex);

lastZeroIndex += 1;

}

}

};

var swap = function(arr, i, j) {

var tmp = arr[i];

arr[i] = arr[j];

arr[j] = tmp;

};

```

**Explain:**

two pointer: index in the loop and last zero index we met.

every time we met a non-zero element, swap it with the last zero element, move the last zero element's index.

every time we met a zero element, log it if we haven't met any zero yet, otherwise just move on and do nothing.

**Complexity:**

* Time complexity : O(n).

* Space complexity : O(1).