Reverse Words in a String

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

For example,

Given s = "the sky is blue",

return "blue is sky the".

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.

 

一次遍历，将所有遇到的单词加在头部。

class Solution {public:    void reverseWords(string &s)     {        string rs = "";        int i = 0;        while(true)        {            // skip leading space            while(i < s.size() && s[i] == ' ')                i ++;            string word = "";            // s[i] points to first non-space            while(i < s.size() && s[i] != ' ')            {                word += s[i];                i ++;            }            if(word != "")                rs = word + " " + rs;            else    // i == s.size()                break;        }        if(rs != "")            rs.erase(rs.end()-1);   // if rs contains words, erase the last space        s = rs;    }};