【LeetCode】Evaluate Reverse Polish Notation

class Solution {public:     int cal(int num1, int num2, string ch){int result;if (ch == "+"){result = num1 + num2;}else if (ch == "-"){result = num1 - num2;}else if (ch == "*"){result = num1*num2;}else if (ch == "/"){result = num1 / num2;}return result;}int evalRPN(vector<string>&temp){int i;stack<int> opd;for (i = 0; i < temp.size(); i++){if (temp[i] == "+" || temp[i] == "-" || temp[i] == "*" || temp[i] == "/"){int right;right = opd.top();opd.pop();int left;left = opd.top();opd.pop();opd.push(cal(left, right, temp[i]));}else{opd.push(atoi(temp[i].c_str()));}}return opd.top();} };