# Question

Formatted question description: https://leetcode.ca/all/283.html

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

Note that you must do this in-place without making a copy of the array.

Example 1:

Input: nums = [0,1,0,3,12]
Output: [1,3,12,0,0]


Example 2:

Input: nums = [0]
Output: [0]


Constraints:

• 1 <= nums.length <= 104
• -231 <= nums[i] <= 231 - 1

Follow up: Could you minimize the total number of operations done?

# Algorithm

To do in-place replacement method, you need to use two pointers, one of which keeps sweeping backwards to find a non-zero position, and then swap positions with the previous pointer.

# Code

• 
public class Move_Zeroes {

// time: O(N)
// space: O(N)
class Solution_swap {
public void moveZeroes(int[] nums) {

if (nums == null || nums.length == 0) {
return;
}

int lastNonZeroAt = 0;
for (int i = 0; i < nums.length; i++) {
if (nums[i] != 0) {
int tmp = nums[lastNonZeroAt];
nums[lastNonZeroAt] = nums[i];
nums[i] = tmp;

lastNonZeroAt++;
}
}
}
}

class Solution {
public void moveZeroes(int[] nums) {
if (nums == null || nums.length == 0) {
return;
}

int actualP = 0;
int scanP = 0;

while (scanP < nums.length) {

if (nums[scanP] != 0) {
nums[actualP++] = nums[scanP++];
} else {
scanP++;
}

}

while (actualP < nums.length) {
nums[actualP++] = 0;
}
}
}

}

############

class Solution {
public void moveZeroes(int[] nums) {
int left = 0, n = nums.length;
for (int right = 0; right < n; ++right) {
if (nums[right] != 0) {
int t = nums[left];
nums[left] = nums[right];
nums[right] = t;
++left;
}
}
}
}

• class Solution:
def moveZeroes(self, nums: List[int]) -> None:
"""
Do not return anything, modify nums in-place instead.
"""
left, n = 0, len(nums)
for right in range(n):
if nums[right] != 0:
nums[left], nums[right] = nums[right], nums[left]
left += 1

############

class Solution(object):
def moveZeroes(self, nums):
"""
:type nums: List[int]
:rtype: void Do not return anything, modify nums in-place instead.
"""
i = j = 0
for i in range(0, len(nums)):
if nums[i] != 0:
nums[j], nums[i] = nums[i], nums[j]
j += 1


• class Solution {
public:
void moveZeroes(vector<int>& nums) {
int left = 0, n = nums.size();
for (int right = 0; right < n; ++right) {
if (nums[right] != 0) {
swap(nums[left], nums[right]);
++left;
}
}
}
};

• func moveZeroes(nums []int) {
n := len(nums)
left := 0
for right := 0; right < n; right++ {
if nums[right] != 0 {
nums[left], nums[right] = nums[right], nums[left]
left++
}
}
}


• /**
Do not return anything, modify nums in-place instead.
*/
function moveZeroes(nums: number[]): void {
const n = nums.length;
let i = 0;
for (let j = 0; j < n; j++) {
if (nums[j]) {
if (j > i) {
[nums[i], nums[j]] = [nums[j], 0];
}
i++;
}
}
}


• /**
* @param {number[]} nums
* @return {void} Do not return anything, modify nums in-place instead.
*/
var moveZeroes = function (nums) {
let left = 0,
n = nums.length;
for (let right = 0; right < n; ++right) {
if (nums[right]) {
[nums[left], nums[right]] = [nums[right], nums[left]];
++left;
}
}
};


• impl Solution {
pub fn move_zeroes(nums: &mut Vec<i32>) {
let mut i = 0;
for j in 0..nums.len() {
if nums[j] != 0 {
if j > i {
nums[i] = nums[j];
nums[j] = 0;
}
i += 1;
}
}
}
}