344. Reverse String

• Difficulty: Easy

• Topics: Two Pointers, String

• Similar Questions:

  • Reverse Vowels of a String

  • Reverse String II

Problem:

Write a function that reverses a string. The input string is given as an array of characters char[].

Do not allocate extra space for another array, you must do this by modifying the input array in-place with O(1) extra memory.

You may assume all the characters consist of printable ascii characters.

Input: ["h","e","l","l","o"]
Output: ["o","l","l","e","h"]

Input: ["H","a","n","n","a","h"]
Output: ["h","a","n","n","a","H"]

Solutions:

class Solution {
public:
    void reverseString(vector<char>& s) {
        int left = 0; 
        int right = s.size() - 1;
        while (left < right) {
            swap(s[left], s[right]);
            ++left;
            --right;
        }
    }
};