LeetCode / ZigZag string conversion

gistfile1.cpp

string convert(string s, int numRows) {
	if (numRows == 0) return "";
	if (numRows == 1) return s;
	vector<string> rows(numRows);
	int row = 0;
	int dir = -1;
	for (int i = 0; i < s.size(); i++) {
		rows[row].push_back(s[i]);
		if (row == numRows - 1 || row == 0) {
			dir = -dir;
		}
		row += dir;
	}
	std::stringstream out;
	for (int i = 0; i < rows.size(); ++i) {
		out << rows[i];
	}
	return out.str();
}