Move Zeroes.cpp

/*
Move Zeroes
===========

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.

Hint #1  
In-place means we should not be allocating any space for extra array. But we are allowed to modify the existing array. However, as a first step, try coming up with a solution that makes use of additional space. For this problem as well, first apply the idea discussed using an additional array and the in-place solution will pop up eventually.

Hint #2  
A two-pointer approach could be helpful here. The idea would be to have one pointer for iterating the array and another pointer that just works on the non-zero elements of the array.
*/

class Solution
{
public:
  void moveZeroes(vector<int> &nums)
  {
    int i = 0, j = 0, n = nums.size();
    while (j < n)
    {
      while (i < n && nums[i] != 0)
        i++;
      while (j < n && nums[j] == 0)
        j++;
      if (j <= i)
        j++;
      else if (j >= n || i >= n)
        break;
      else
        swap(nums[i], nums[j]);
    }
  }
};