LeetCode OJ - Reverse Words in a String

题目：

　　Given an input string, reverse the string word by word.

　　For example,
　　Given s = "the sky is blue",
　　return
"blue is sky the".

解题思路：

　　1、先对字符串进行一次总的翻转

　　2、以空格为单位，划分单词，然后对每个单词再进行一次翻转

代码：

class Solution {

public:

    void swap(char& a, char& b){

        int tmp = a;

        a = b;

        b = tmp;

    }

    void reverse(string &s, int begin, int end){

        if (s[begin] == ‘\0‘ || s[end] == ‘\0‘){

            return;

        }

        while (begin < end){

            swap(s[begin], s[end]);

            begin++;

            end--;

        }

    }

    void reverseWords(string &s) {

        if (s[0] == ‘\0‘ || s.empty()){

            return;

        }

        reverse(s, 0, s.length() - 1);

        //*/

        int start = 0, end = 0, len = 0;

        while (start < s.length()){

            while (start != s.length() && s[start] == ‘ ‘) start++; //跳过对于的空格

            for (end = start; end != s.length() && s[end] != ‘ ‘; end++);

            if (len != 0 && end > start) s[len++] = ‘ ‘;

            if (end > start){

                reverse(s, start, end - 1);

            }

            while (start < end) s[len++] = s[start++];

}

        s.resize(len);

        //*/

    }

};

LeetCode OJ - Reverse Words in a String