LeetCode 344. Reverse string

https://leetcode-cn.com/problems/reverse-string/

Ideas :

1. Double pointer , Head pointer and tail pointer
2. When the head pointer index is smaller than the tail pointer index , Exchange value

 /** *  Double pointer  * @param s */
    public void reverseString(char[] s) {
    
        int first = 0;
        int last = s.length - 1;
        while (first < last) {
    
            char tmp = s[first];
            s[first] = s[last];
            s[last] = tmp;
            first++;
            last--;
        }
    }