package com.zmz.algorithm.stackQueue;

import java.util.Stack;

/**
 * @author 张明泽
 * Create by 2022/5/31 23:04
 * 逆波兰表达式求值
 * LeetCode-150
 */
public class EvaluateInverseExpression {
    public static void main(String[] args) {
        String[] tokens = {"4","13","5","/","+"};
        int result = evalRPN(tokens);
        System.out.println(result);
    }
    public static int evalRPN(String[] str) {
        Stack<Integer> stack = new Stack<>();
        for (String s : str) {
            if (s.equals("+")) {
                stack.push(stack.pop() + stack.pop());
            } else if  (s.equals("-")) {
                int temp = stack.pop();
                stack.push(stack.pop() - temp);
            } else if (s.equals("*")) {
                stack.push(stack.pop() * stack.pop());
            } else if (s.equals("/")) {
                int temp = stack.pop();
                stack.push(stack.pop() / temp);
            }
            else {
                stack.push(Integer.valueOf(s));
            }
        }
        return stack.pop();
    }
}