150 逆波兰表达式求值

https://leetcode.cn/leetbook/read/top-interview-questions-medium/xwaiag/

cost: 14m46s

class Solution {
public:
    int evalRPN(vector<string>& tokens) {
        stack<int> operands;
        int res = 0;
        auto getOperands = [&operands] {
            int v2 = operands.top();
            operands.pop();
            int v1 = operands.top();
            operands.pop();
            return tuple<int, int>(v1, v2);
        };
        for (const string& token : tokens) {
            if (token == "+") {
                auto [v1, v2] = getOperands();
                v1 += v2;
                operands.push(v1);
            } else if (token == "-") {
                auto [v1, v2] = getOperands();
                v1 -= v2;
                operands.push(v1);
            } else if (token == "*") {
                auto [v1, v2] = getOperands();
                v1 *= v2;
                operands.push(v1);
            } else if (token == "/") {
                auto [v1, v2] = getOperands();
                v1 /= v2;
                operands.push(v1);
            } else {
                int v = std::stoi(token);
                operands.push(v);
            }
        }
        return operands.top();
    }
};