Problem description:

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:

The idea is to use a pointer to store the position of zeros, another point to walk through the array.

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

time complexity: $O(n)$

reference: