LeetCodeOJ--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.

C++版本：

class Solution {
public:
    void reverseWords(string &s) {
    string rs;
    for (int i = s.length()-1; i >= 0; )
    {
        while (i >= 0 && s[i] == ' ') {i--;}
        if (i < 0) {break;}
        if (!rs.empty()) {rs.push_back(' ');}
        string t;
        while (i >= 0 && s[i] != ' ') {t.push_back(s[i--]);}
        reverse(t.begin(), t.end());
        rs.append(t);
    }
    s = rs;
    }
};