/* *****************************************************************************
 * %{QMAKE_PROJECT_NAME}
 * Copyright (c) %YEAR% killerbee
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <https://www.gnu.org/licenses/>.
 * ****************************************************************************/
#include <algorithm>
#include <numeric>
#include <string>
#include <vector>
using std::string;
using std::vector;

bool is_number(const std::string& op);

class Solution {
 public:
	int calPoints(vector<string>& ops) {
		std::vector<int> nums;
		for (std::size_t i{}; i < ops.size(); ++i) {
			if (is_number(ops[i])) {
				// record a new score
				nums.push_back(std::stoi(ops[i]));
			} else {
				if (ops[i] == "+") {
					// record a new score that is the sum of the previous two scores
					// it is guaranteed there will always be two previous scores
					nums.push_back(nums[nums.size() - 1] + nums[nums.size() - 2]);
				} else if (ops[i] == "D") {
					// record a new score that is double the previous score
					// it is guaranteed there will always be a previous score
					nums.push_back(nums.back() * 2);
				} else if (ops[i] == "C") {
					// invalidate the previous score, removing it from the record
					// it is guaranteed there will always be a previous score
					nums.pop_back();
				}
			}
		}

		return std::accumulate(nums.begin(), nums.end(), 0);
	}
};

bool is_number(const std::string& op) {
	// first check if number starts with a sign character
	std::size_t i = 0;
	if (op[0] == '-' || op[0] == '+') {
		i = 1;
	}
	for (; i < op.length(); ++i) {
		if (! std::isdigit(op[i])) {
			return false;
		}
	}
	return true;
}