// @Title: 逆波兰表达式求值 (Evaluate Reverse Polish Notation)
// @Author: qisiii
// @Date: 2024-09-14 13:21:52
// @Runtime: 7 ms
// @Memory: 43.6 MB
// @comment: 
// @flag: 
class Solution {
    public int evalRPN(String[] tokens) {
        Stack<String> stack = new Stack<>();
        for (String token : tokens) {
            if (token.equals("+")) {
                Integer second = Integer.valueOf(stack.pop());
                Integer first = Integer.valueOf(stack.pop());
                stack.push(String.valueOf(first + second));
            } else if (token.equals("-")) {
                Integer second = Integer.valueOf(stack.pop());
                Integer first = Integer.valueOf(stack.pop());
                stack.push(String.valueOf(first - second));
            } else if (token.equals("*")) {
                Integer second = Integer.valueOf(stack.pop());
                Integer first = Integer.valueOf(stack.pop());
                stack.push(String.valueOf(first * second));
            } else if (token.equals("/")) {
                Integer second = Integer.valueOf(stack.pop());
                Integer first = Integer.valueOf(stack.pop());
                stack.push(String.valueOf(first / second));
            } else {
                stack.push(token);
            }
        }
        return Integer.valueOf(stack.peek());
    }
}