题解 | #逆波兰表达式求值#

#include<iostream>
#include<algorithm>
#include<vector>
#include<stack>
#include<string>

using namespace std;

//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
     */
    int evalRPN(vector<string>& tokens) {
        // write code here
        stack<int> stk;
        for (int i = 0; i < tokens.size(); i++) {
            char ch;
            bool flag = 0;
            if (tokens[i] == "*" || tokens[i] == "+" || tokens[i] == "-" || tokens[i] == "/") {
                int a = stk.top();
                stk.pop();
                int b = stk.top();
                stk.pop();
                if (tokens[i] == "*")
                    stk.push(a * b);
                else if (tokens[i] == "+")
                    stk.push(a + b);
                else if (tokens[i] == "-")
                    stk.push(b - a);
                else
                    stk.push(b / a);
            }  
            else {
                int k = stoi(tokens[i]);
                stk.push(k);
            }
        }
        return stk.top();
    }
    int main() {
        vector<string> tokens = { "2","1","+","4","*" };
        int result = evalRPN(tokens);
        cout << result;
        return 1;
    }
//};