题解 | #逆波兰表达式求值#

#include <stack>
class Solution {
  public:
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     *
     * @param tokens string字符串vector
     * @return int整型
     */
    void calculate(stack<int>& sk, string symbol) {
        int num1 = sk.top();
        sk.pop();
        int num2 = sk.top();
        sk.pop();
        if (symbol == "+") {
            sk.push(num2 + num1);
        } else if (symbol == "-") {
            sk.push(num2 - num1);
        } else if (symbol == "*") {
            sk.push(num2 * num1);
        } else if (symbol == "/") {
            sk.push(num2 / num1);
        }
    }
    int evalRPN(vector<string>& tokens) {
        stack<int> sk;
        for (int i = 0; i < tokens.size(); i++) {
            if (tokens[i] == "+" || tokens[i] == "-" || tokens[i] == "*" ||
                    tokens[i] == "/") {
                calculate(sk, tokens[i]);
            } else {
                sk.push(stoi(tokens[i]));
            }
        }
        return sk.top();
    }
};