Time Complexity: O(N), where N is the length of the string. We perform N push operations and N pop operations.

Space Complexity: O(N), due to the stack storing all N characters of the input string.

Optimal Approach

Algorithm

To reverse a string, we can visualize the problem as a sequence of swaps. The character at the beginning of the string needs to be swapped with the character at the end. Then the second character with the second-last character, and so on. This continues until we reach the middle of the string. This concept can be implemented effectively using the two-pointer technique.

Initialize two pointers: one pointing to the start of the string and the other to the end.
Loop until the two pointers cross (i.e., while the left pointer is less than the right pointer).
In each iteration, swap the characters at the two pointers.
Move the left pointer one step to the right and the right pointer one step to the left.