It's crucial to see that how both indices were moving in conjunction, and how they depend on each other.

We kept moving the pointers until we got the sum that matches the target value-- or until we reached the middle of the array, and no combinations were found.

The time complexity of this solution is O(n) and space complexity is O(1), a significant improvement over our first implementation!

Another Example

In addition, to the previous example, the two pointer technique can also involve the pattern of using a fast pointer and a slow pointer.

1let fast = slow = head;