[151] Reverse Words in a String

题目：Reverse Words in a String

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Given an input string s, reverse the string word by word. For example, given s = “the sky is blue”, return “blue is sky the”.

题意：

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题意很明确，将字符串中的单词进行翻转，形成新的字符串。但是这其中有几个问题我们需要思考（参考leetCode官方CleanCodeBook）：

Q: What constitutes a word? A: A sequence of non-space characters constitutes a word.

Q: Does tab or newline character count as space characters? A: Assume the input does not contain any tabs or newline characters.

Q: Could the input string contain leading or trailing spaces? A: Yes. However, your reversed string should not contain leading or trailing spaces.

Q: How about multiple spaces between two words? A: Reduce them to a single space in the reversed string.

解法：

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class Solution {
public:
	void reverseWords(std::string &s) {
		
	   std::string reversed("");
		int j = s.length();

		for (int i = s.length() - 1; i >= 0; --i) {
			if(s.at(i) == ' ') j = i;
			else if (i == 0 || s.at(i - 1) == ' ') {
				if (reversed.length() != 0) reversed += ' ';
				reversed += s.substr(i, j - i);
			}
		}
		s = reversed;
	}
}