//time:o(n)

//space:o(1)

class Solution {

// num of operation : nums.length;

public void moveZeroes(int[] nums) {

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

int start = 0;

for (int i = 0; i < nums.length; i++) {

if (nums[i] != 0) {

nums[start++] = nums[i];

//nums[start]=nums[i];

//start++;

}

}

while (start < nums.length) {

nums[start++] = 0;

}

}

// num of operation : 2 * num of non-zero

// lots of zeros

public void moveZeroes2(int[] nums) {

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

for (int i = 0, j = 0; i < nums.length; i++) {

if (nums[i] != 0) {

int temp = nums[i];

nums[i] = nums[j];

nums[j++] = temp;

}

}

}

}