344. Reverse String

1. Description

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.

2. Example

Example 1:
Input: [“h”,“e”,“l”,“l”,“o”]
Output: [“o”,“l”,“l”,“e”,“h”]

Example 2:
Input: [“H”,“a”,“n”,“n”,“a”,“h”]
Output: [“h”,“a”,“n”,“n”,“a”,“H”]

3. Solutions

My Accepted Solution

n = m_str.size()
Time complexity: O(n)
Space complexity: O(1)

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