leetcode Reverse Words in a String

题目连接

https://leetcode.com/problems/reverse-words-in-a-string/ 

Reverse Words in a String

Description

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

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

class Solution {
public:
	void reverseWords(string &s) {
		n = s.length();
		string x = "";
		reverse(s.begin(), s.end());
		while (!op.empty()) op.pop();
		for (size_t i = 0; i < n;) {
			while (i < n && s[i] == ' ') i++;
			if (i == n) break;
			while (i < n && s[i] != ' ') { op.push(s[i++]); }
			while (!op.empty()) { x += op.top(); op.pop(); }
			x += ' ';
		}
		if (x.length()) x.pop_back();
		s = x;
	}
private:
	size_t n;
	stack<char> op;
};