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
        int tmp=0;
        Stack<Integer> stack=new Stack<>();
        int n = tokens.length;
        int x;
        for(int i=0;i<n;i++){
            switch(tokens[i]){
                case "+":
                    tmp = stack.pop()+stack.pop();
                    stack.push(tmp);
                    break;
                case "-":
                    x=stack.pop();
                    tmp = stack.pop()-x;
                    stack.push(tmp);
                    break;
                case "*":
                    tmp = stack.pop()*stack.pop();
                    stack.push(tmp);
                    break;
                case "/":
                    x=stack.pop();
                    tmp = stack.pop()/x;
                    stack.push(tmp);
                    break;
                default:
                    stack.push(Integer.parseInt(tokens[i]));
            }
        }
        return stack.pop();
    }
}