#栈与队列 #逆波兰表达式求值

evaluate-reverse-polish-notation.cpp

class Solution {
public:
    int evalRPN(vector<string>& tokens) {
        stack<int> nums;
        for (const auto& op : tokens) {
            if (op == "+" || op == "-" || op == "*" || op == "/") {
                int rht = nums.top();
                nums.pop();
                int lft = nums.top();
                nums.pop();
                if (op == "+") nums.push(lft + rht);
                if (op == "-") nums.push(lft - rht);
                if (op == "*") nums.push(lft * rht);
                if (op == "/") nums.push(lft / rht);
            } else {
                nums.push(stoi(op));
            }
        }
        return nums.top();
    }
};