leetcode - 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.

// 主要用到两个字符串，string t,res,扫描整个字符串，将单词copy to t.如果，遇到空格，将cache t字符串copy to res
// 重复上面的步骤，直到i = s.length,最后一步就是temp可能包含字符串，所以，再次copy to res.
// 时间复杂度 O(n)  空间复杂度 O(1). 这题已经AC.
class Solution {
public:
    void reverseWords(std::string &s) {
		std::string t = "",res = "";
		for(std::string::size_type i = 0; i < s.length(); i++)
		{
			if(s[i] == ' ')
			{
				res = t + (t == ""||res ==""?"":" ") + res;
				t = "";
			}
			else
			{
				t += s[i];
			}
		}
		s = t + (t == ""||res == ""?"":" ") + res;
		std::cout << s << std::endl;
	}
};