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".

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.

class Solution {
public:
    void reverseWords(string &s) 
    {
        int length=s.length();
        if(length==0) return;
        
        string result;
        int index=0;
        while(true)
        {
            while(s[index]==' ' && index<length) index++;
            if(index==length) break;
            string word;
            while(s[index]!=' ' && index<length) word=word+s[index++];
            if(result=="") result=word;
            else result=word+" "+result;
        }
        s=result;
    }
};