class Solution {
public:
	void reverseString(vector<char>& s) {
		if (s.size() == 1) {
			return;
		}
		for (int i = 0; i <= (s.size() - 2) / 2; ++i) {
			swap(s[s.size() - 1 - i], s[i]);
		}
	}
};