27. Reverse a String

The problem can be found at the following link: Question Link

My Approach

Simply used a two-pointer approach to reverse the given string.

• I initialized two pointers, i and j, to the start and end of the string respectively.

• I swapped the characters at these pointers and moved i forward and j backward until they met in the middle of the string.

Time and Auxiliary Space Complexity

• Time Complexity: The time complexity of this algorithm is O(N/2), where N is the length of the input string. This is because we only need to swap characters up to the middle of the string.

• Auxiliary Space Complexity: The algorithm uses only a constant amount of extra space for the two pointers and the swapping operation, so the space complexity is O(1).

Code (C++)

class Solution
{
public:
    string reverseWord(string str)
    {
        int i = 0, j = str.size() - 1;
        while (i < j)
        {
            swap(str[i], str[j]);
            ++i;
            --j;
        }

        return str;
    }
};

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