Reverse Words in a String II -- LeetCode

Given an input string, reverse the string word by word. A word is defined as a sequence of non-space characters.

The input string does not contain leading or trailing spaces and the words are always separated by a single space.

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

Could you do it in-place without allocating extra space?

思路：这题比另一个reverse words要简单，因为不存在多余空格的问题。

因此in-place方法很简单，先把整个字符串反转，然后依次把字符串中的每个单词再反转一次。

class Solution {
public:
    void reverseWords(string &s) {
        int l = 0, r = s.size() - 1;
        while (l < r)
            swap(s[l++], s[r--]);
        for (int i = 0, n = s.size(); i < n;)
        {
            for (r = i + 1; r < n && s[r] != ' '; r++);
            l = i, r--;
            i = r + 2;
            while (l < r)
                swap(s[l++], s[r--]);
        }
    }
};