INTUITION:

The idea behind the two pointers approach is that we can shift all non-zero elements to the front of the array in a single pass. If we swap non-zero elements into their correct positions as we iterate through the array, the zeroes will automatically be pushed to the back.

APPROACH:

• Two pointers (left and right):
  • right pointer iterates over the array to examine each element.
  • left pointer tracks the position where the next non-zero element should go.
• For each element:
  • If nums[right] is non-zero, it swaps with nums[left] and increments left.
  • This way, non-zero elements are pushed towards the beginning, and the zeroes are automatically pushed towards the end.

Time Complexity:O(N)

Space Complexity:O(1)

Here’s the code:

class Solution {
public:
    void moveZeroes(vector<int>& nums) {
        int left = 0; // Initialize left pointer to 0
        for (int right = 0; right < nums.size(); right++) {
            if (nums[right] != 0) {
                swap(nums[right], nums[left]); // Swap non-zero element with the element at left pointer
                left++; // Increment the left pointer
            }
        }
    }
};

KEYPOINTS:

• Swap Only When Necessary: Swap only when a non-zero element is found.
• Order Preservation: Non-zero elements maintain their relative order.
• Zero Shift: Zeroes are naturally pushed to the end by the swaps, without any extra operations.