Move Zeroes

Problem

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.

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

Constraints

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

Solution

The problem Move Zeroes can be solved using a sliding window technique by tracking the position of the first occurrence of 0 from the array with a left index and the position of the first non zero element starting from the left index with a right index. By swapping elements at left and right indexes until the right index reaches the end, all 0’s can be moved to the end while also maintaining the relative order of the non-zero elements.

Implementation

class Solution
{
  public:
    void moveZeroes(vector<int> &nums)
    {
        int left = 0;
        while (left < nums.size() - 1 && nums[left] != 0)
            left += 1;

        int right = left + 1;
        while (right < nums.size())
        {
            while (right < nums.size() - 1 && nums[right] == 0)
                right += 1;

            swap(nums[left++], nums[right++]);
        }
    }
};