刷leetcode的第一道题——Reverse Words in a String

好久没在Online Judge上做题了，今晚7点就要做阿里校招的在线笔试了，前两个多小时去leetcode做了一道字符串的题，好多潜在的trick，还好在WA了两次后终于AC了。

Leetcode第一题Reverse Words in a String，题目很简单：

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

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

第一次没点题目的详细说明，总结trick：

1、前导和后导空格需要去掉，中间多个空格只能保留一个（话说这还是我上次实习面有道的一道题目）

2、字符串只有空格时，返回""

下面贴上代码，基本上用到的字符串函数都是自己手动实现的（除memmove外），Leetcode的接口居然定义的是string，下面代码的实现都是char*

class Solution {public:    void reverseWords(string &s) {        if(s.length() == 0 || s == " "){            s = "";            return;        }        int cnt = 0;        for(int i = 0 ; i < s.length(); i ++){            if(s[i] == ' ')                cnt ++;            else                break;        }        if(cnt == s.length()){           s = "";           return;        }        char str[10240];        strcpy(str ,s.c_str());        strtrim(str);        int len = strlength(str);        int begin = 0;        for (int i = 0; i < len; i ++) {            if (str[i] == ' ') {                reverse(str,begin,i - 1);                begin = i + 1;            }        }        reverse(str, begin, len - 1);        reverse(str,0,len-1);        for (int i = 0; i < len ; i ++) {           s[i] = str[i];        }        s.resize(len);    }    int strlength(const char *str){        const char *pstr = str;        while (*pstr ++ != '\0');        return pstr - str - 1;    }    void swap(char &a,char &b) {        char tmp = a;        a  = b;        b = tmp;    }    void strtrim(char *str){//去除空格        char *pstr = str;        int len = strlen(str);        int from = 0, to = 0;        while(*pstr == ' ') {            pstr++;            from ++;        }        pstr = str + len - 1;        while(*pstr == ' ') {            pstr --;            to ++;        }        memmove(str,str+from,len - from - to);        *(str + len - from - to) = '\0';        pstr = str;        char *ts = str;        while(*pstr != '\0'){            if(*pstr != ' '){                *ts = *pstr;                ts++;                pstr++;            }else{                while(*pstr == ' ') pstr ++;                *ts ++ = ' ';            }        }        *(ts++) = '\0';    }    void reverse(char *str, int from, int to) {        char *pbegin = str + from;        char *pend = str + to;        while (pbegin <= pend) {            swap(*pbegin++, *pend --);        }    }};

代码写的不好，'\0'截断问题谁能给指导一下。