题解 | #逆波兰表达式求值#

import java.util.*;


public class Solution {
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     * 
     * @param tokens string字符串一维数组 
     * @return int整型
     */
    public int evalRPN (String[] tokens) {
        // write code here
        Stack<String> stack = new Stack<>();
        int temp = 0;
        for (int i = 0; i < tokens.length; i++) {
            switch (tokens[i]) {
                case "+": 
                temp = Integer.parseInt(stack.pop()) + Integer.parseInt(stack.pop());
                stack.push(temp + "");
                break;
                case "-": 
                temp = Integer.parseInt(stack.pop());
                temp = Integer.parseInt(stack.pop()) - temp;
                stack.push(temp + "");
                break;
                case "*": 
                temp = Integer.parseInt(stack.pop()) * Integer.parseInt(stack.pop());
                stack.push(temp + "");
                break;
                case "/": 
                temp = Integer.parseInt(stack.pop());
                temp = Integer.parseInt(stack.pop()) / temp;
                stack.push(temp + "");
                break;
                default:
                stack.push(tokens[i]);
            }
        }
        return Integer.parseInt(stack.pop());
    }
}