[LeetCode]Reverse Words in a String

原题链接：http://oj.leetcode.com/problems/reverse-words-in-a-string/

题目描述：

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

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

click to show clarification.

Clarification:

• What constitutes a word?
  A sequence of non-space characters constitutes a word.
• Could the input string contain leading or trailing spaces?
  Yes. However, your reversed string should not contain leading or trailing spaces.
• How about multiple spaces between two words?
  Reduce them to a single space in the reversed string.

题解：

　　这道题真的很简单，尤其是用Java、C#这种对字符串操作的封装已经很强大的语言来写。我是用的C++来写的，稍微麻烦一点点。

string Rtrim( string &str ){
        str.erase(std::find_if(str.rbegin(), str.rend(),std::not1(std::ptr_fun(::isspace))).base(),str.end());  
        return str;  
    }
    void reverseWords(string &s){
        vector<string> strs;
        int len = s.length();
        int start,end;
        bool flag = false;
        for(int i=0; i<len; i++){
            if(s[i]!=' ' && !flag){
                start = i;
                flag = true;
            }else if(s[i]==' ' && flag){
                end = i;
                flag = false;
                strs.push_back(s.substr(start,end-start));
            }
        }
        if(flag){
            strs.push_back(s.substr(start,len-start));
        }
        s = "";
        while( !strs.empty() ){
            s+=strs.back();
            s+=" ";
            strs.pop_back();
        }
        s = Rtrim(s);
    }