Reverse String

Description

Write a function that reverses a string. The input string is given as an array of characters s.↳

You must do this by modifying the input array in-place with O(1) extra memory.↳

Example 1:

Input: s = [“h”,“e”,“l”,“l”,“o”] Output: [“o”,“l”,“l”,“e”,“h”]

Example 2:

Input: s = [“H”,“a”,“n”,“n”,“a”,“h”] Output: [“h”,“a”,“n”,“n”,“a”,“H”]

Constraints:

• 1 <= s.length <= 105
• s[i] is a printable ascii character.

Code

Time Complexity: $O(n)$, Space Complexity: $O(1)$

class Solution {
public:
    void reverseString(vector<char>& s) {
        int n = s.size();
        for(int i = 0; i < n / 2; i++) {
            swap(s[i], s[n - 1 - i]);
        }
    }
};

Source

• Reverse String - LeetCode