Evaluate Reverse Polish Notation 求RPN的值@LeetCode

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用一个Stack就很容易做到了，这道题的最大发现是：这道题是2013-11-27发布出来的，到今天，短短半个月内，居然提交量快到了1万！！！

居然有这么多人都在刷题！！压力山大！

package Level3;import java.util.Stack;/** *  * Evaluate Reverse Polish Notation  *  * Evaluate the value of an arithmetic expression in Reverse Polish Notation.Valid operators are +, -, *, /. Each operand may be an integer or another expression.Some examples:  ["2", "1", "+", "3", "*"] -> ((2 + 1) * 3) -> 9  ["4", "13", "5", "/", "+"] -> (4 + (13 / 5)) -> 6Discuss * */public class S142 {public static void main(String[] args) {String[] tokens = {"4", "13", "5", "/", "+"};System.out.println(evalRPN(tokens));}public static int evalRPN(String[] tokens) {        Stack<String> stack = new Stack<String>();        for(int i=0; i<tokens.length; i++){        if(tokens[i].equals("+")){        int val = Integer.parseInt(stack.pop()) + Integer.parseInt(stack.pop());        stack.push(String.valueOf(val));        }else if(tokens[i].equals("-")){        int v1 = Integer.parseInt(stack.pop());        int v2 = Integer.parseInt(stack.pop());        int val = v2 - v1;        stack.push(String.valueOf(val));        }else if(tokens[i].equals("*")){        int val = Integer.parseInt(stack.pop()) * Integer.parseInt(stack.pop());        stack.push(String.valueOf(val));        }else if(tokens[i].equals("/")){        int v1 = Integer.parseInt(stack.pop());        int v2 = Integer.parseInt(stack.pop());        int val = v2 / v1;        stack.push(String.valueOf(val));        }else{        stack.push(tokens[i]);        }        }                return Integer.parseInt(stack.pop());    }}

现在的提交量超过10万！

import java.util.*;public class Solution {    public int evalRPN(String[] tokens) {        Stack<String> stack = new Stack<String>();                for(String s : tokens) {            if(s.equals("+") || s.equals("-") || s.equals("*") || s.equals("/")) {                int second = Integer.parseInt(stack.pop());                int first = Integer.parseInt(stack.pop());                if(s.equals("+")) {                    stack.push(String.valueOf(first+second));                } else if(s.equals("-")) {                    stack.push(String.valueOf(first-second));                } else if(s.equals("*")) {                    stack.push(String.valueOf(first*second));                } else if(s.equals("/")) {                    stack.push(String.valueOf(first/second));                }            } else {                stack.push(s);            }        }                return Integer.parseInt(stack.pop());    }}

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