150.逆波兰表达式求值

两天宇宙人

2020-02-16

🥩stack

class Solution {
public:
    int evalRPN(vector<string>& tokens) {
        stack<int> stk;
        for(auto c : tokens)
        {
            int nu = atoi(c.c_str());
            if(!nu && c != "0") {
                int a = stk.top();
                stk.pop();
                int b = stk.top();
                stk.pop();
                if(c == "+") {
                    stk.push(a + b);
                }
                else if (c == "-") {
                    stk.push(b - a);
                }
                else if (c == "/"){
                    stk.push(b / a);
                }
                else {
                    stk.push(b * a);
                }
            } 
            else 
                stk.push(nu);
        }
        return stk.top();
    }
};