LeetCode - Refresh - Reverse Words in a String II

Reverse in place:

1. reverse the whole sentence.

2. reverse every word.

We cant do it for I, because there are extra spaces in sentence.

class Solution {
public:
    void reverse(string &s, int start, int end) {
        while (start < end) {
            [](char &a, char &b) {char c = a; a = b; b = c;}(s[start++], s[end--]);
        }
    }
    void reverseWords(string &s) {
        int len = s.size(), index = 0;
        reverse(s, 0, len-1);
        for (int i = 0; i < len; i++) {
            if (s[i] == ' ') {
                reverse(s, index, i-1);
                index = i+1;
            }
        }
        reverse(s, index, len-1);
    }
};