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) { // 存储数组数字 遇到运算符时出栈运算 Stack<Integer> stack = new Stack<>(); for (String token : tokens) { switch (token) { case "+" : stack.push(stack.pop() + stack.pop()); break; case "-" : Integer val1 = stack.pop(); stack.push(stack.pop() - val1); break; case "*" : stack.push(stack.pop() * stack.pop()); break; case "/" : Integer val2 = stack.pop(); stack.push(stack.pop() / val2); break; default: stack.push(Integer.valueOf(token)); } } return stack.pop(); } }