表达式求值

表达式求值

时间限制：3000 ms  |  内存限制：65535 KB

难度：4

描述

ACM队的mdd想做一个计算器，但是，他要做的不仅仅是一计算一个A+B的计算器，他想实现随便输入一个表达式都能求出它的值的计算器，现在请你帮助他来实现这个计算器吧。
比如输入：“1+2/4=”，程序就输出1.50（结果保留两位小数）

输入

第一行输入一个整数n，共有n组测试数据（n<10)。
每组测试数据只有一行，是一个长度不超过1000的字符串，表示这个运算式，每个运算式都是以“=”结束。这个表达式里只包含+-*/与小括号这几种符号。其中小括号可以嵌套使用。数据保证输入的操作数中不会出现负数。
数据保证除数不会为0

输出

每组都输出该组运算式的运算结果，输出结果保留两位小数。

样例输入

21.000+2/4=((1+2)*5+1)/4=

样例输出

1.504.00

import java.util.Scanner;import java.util.Stack;public class Main {public static void main(String[] args) {Scanner scanner = new Scanner(System.in);int number = scanner.nextInt();String cc = scanner.nextLine();while (number-- != 0) {String string = scanner.nextLine();Stack<Character> stack = new Stack<Character>();StringBuilder suffix = new StringBuilder("");for (int i = 0; i < string.length(); i++) {char temp = string.charAt(i);if ((temp >= '0' && temp <= '9') || temp == '.') {suffix.append(temp);} else {if (temp == '+' || temp == '-') {suffix.append(" ");if (stack.isEmpty()) {stack.push(temp);} else {char top = stack.peek();if (top == '(') {stack.push(temp);} else {while (!stack.isEmpty() && stack.peek() != '(') {suffix.append(stack.pop() + " ");}stack.push(temp);}}} else if (temp == '*' || temp == '/') {suffix.append(" ");if (stack.isEmpty()) {stack.push(temp);} else {char top = stack.peek();if (top == '+' || top == '-' || top == '(') {stack.push(temp);} else if (top == '*' || top == '/') {suffix.append(stack.pop() + " ");stack.push(temp);}}} else if (temp == '(') {stack.push(temp);} else if (temp == ')') {char top = stack.pop();while (top != '(') {suffix.append(" " + top);top = stack.pop();}} else if (temp == '=') {while (!stack.isEmpty()) {suffix.append(" " + stack.pop());}suffix.append(" " + "=");}}}Stack<Double> result = new Stack<Double>();String arr[] = suffix.toString().split(" ");for (int j = 0; j < arr.length; j++) {char temp = arr[j].charAt(0);double value = 0;if (temp >= '0' && temp <= '9') {value = Double.valueOf(arr[j]);result.push(value);} else if (temp == '+') {double one = result.pop();double two = result.pop();double three = one + two;result.push(three);} else if (temp == '-') {double one = result.pop();double two = result.pop();double three = two - one;result.push(three);} else if (temp == '*') {double one = result.pop();double two = result.pop();double three = one * two;result.push(three);} else if (temp == '/') {double one = result.pop();double two = result.pop();double three = two / one;result.push(three);} else if (temp == '=') {System.out.printf("%.2f\n", result.pop());}}}}}