344. Reverse String

题意：直接反转字符串

class Solution {public:    string reverseString(string s) {    if(s.length()<=1)return s;    int len=s.length(),start=0;    while(start<len-1)    {        char temp=s[start];        s[start]=s[len-1];        s[len-1]=temp;        start++;        len--;    }    return s;    }};