Leetcode 557. Reverse Words in a String III

题目：Given a string, you need to reverse the order of characters in each word within a sentence while still preserving whitespace and initial word order.
Example 1:
Input: “Let’s take LeetCode contest”
Output: “s’teL ekat edoCteeL tsetnoc”
Note: In the string, each word is separated by single space and there will not be any extra space in the string.

面CVTE的实习的时候抽到了一道题跟这道题目类似，我抽到的题目是要把单词的位置对调，比如you are dog就变成dog are you.

这道题的代码如下：

class Solution {public:    string inv(string str){        for(int i = 0; i < str.length()/2; i++)        {            char tmp;            tmp = str[i];            str[i] = str[str.length()-1-i];            str[str.length()-1-i] = tmp;        }        return str;    }    string reverseWords(string s) {        int begin = 0, end = 0;        string res = "";        while(end < s.length()){            while(end != s.length()-1 && s[end] != ' '){                end++;            }            if(end != s.length()-1)                res += inv(s.substr(begin, end-begin)) + " ";            else                res += inv(s.substr(begin, end+1-begin));            begin = end+1;            end++;        }        return res;    }};