最近想把这破机 装成WIN7 想想还是算了 ... 反正用的机会也不多。
不过 发现了一些 想念的东西
从前的作业.
从前的记忆.
package org.lmz; import java.util.Queue;
import java.util.Scanner;
import java.util.Stack;
import java.util.concurrent.LinkedBlockingQueue; public class calculator_test { static String operator = "+-*/%^()"; /**
* 预处理表达式，正、负号前加0(如果一个加号（减号）出现在最前面或左括号后面，则该加号（减号）为正负号) 比如 -1-(-1+1) 这种表达式 会处理成 0-1-(0-1+1)
*/
public static String pretreatment(String str) {
StringBuffer sb = new StringBuffer(str);
for (int i = 0; i < sb.length(); i++) {
char c = sb.charAt(i);
if (operator.indexOf(c) >= 0) {
if (i == 0) {
sb.insert(0, '0');
i++;
} else if (sb.charAt(i - 1) == '(') {
sb.insert(i, '0');
i++;
}
}
}
return sb.toString();
} /***
* 0 优先级相等 ； -1 op1 优先级大于op2； 1 op2 优先级大于 op1
*/
public static int opcompare(char op1, char op2) {
if (op1 == '(') { // 遇到括号 就直接入栈 所以 op2 大
return 1;
}
if ('^' == op1) {
if (op2 == '^') {
return 0;
}
return -1;
} else if ("+-".indexOf(op1) >= 0) {
if ("+-".indexOf(op2) >= 0) {
return 0;
}
return 1;
} else // if("*/%".indexOf(op1) >=0) 没必要 再判断是否为 */% 了
{
if ("+-".indexOf(op2) >= 0) {
return -1;
} else if ('^' == op2) {
return 1;
}
return 0;
}
}
/**
* 计算传入的算术表达式
*/
public static double Calculator2(String s) throws Exception {
//预处理式子
String prestr = pretreatment(s);
//用于保存 逆波兰式 的队列
LinkedBlockingQueue<String> polish = new LinkedBlockingQueue<String>();
// 拼接 数字 char ---> numble
StringBuffer temp = new StringBuffer(); Stack<Character> stack = new Stack<Character>();
for (int i = 0; i < prestr.length(); i++) { char c = prestr.charAt(i);
//如果找到 操作符
if (operator.indexOf(c) >= 0) {
if (temp.length() > 0) {//如果 有数字 就压栈
polish.offer(temp.toString());
temp = new StringBuffer();
}
switch (c) {
case '(':
stack.push(c);
break;
case ')':
while (stack.size() > 0) {
char op = stack.pop();
if (op != '(') {
polish.offer(String.valueOf(op));
} else {
break;
}
}
break;
default:
if (stack.size() == 0) {
stack.push(c);
} else {
while (stack.size() > 0) {
char op1 = stack.lastElement();
int com = opcompare(op1, c);
if (com <= 0) {
polish.offer(String.valueOf(stack.pop()));
} else {
stack.push(c);
break;
}
}
if (stack.size() == 0) {
stack.push(c);
}
}
break;
}
} else {
temp.append(c);
}
}
if (temp.length() > 0) {
polish.offer(temp.toString());
}
while (stack.size() > 0) {
polish.offer(String.valueOf(stack.pop()));
}
System.out.println("Calcstra Queue:" + polish.toString()); return CalcstraWithQueue(polish);
}
/**
* 计算 逆波兰表达式 用队列表示
* @throws Exception 各种错误都有可能
*/
public static double CalcstraWithQueue(Queue<String> que) throws Exception {
Stack<Double> stack = new Stack<Double>();
while(true)
{
String str = que.poll();
if(str == null)
{
break;
}
if (operator.indexOf(str) >= 0) { double num2 = stack.pop();
double num1 = stack.pop();
double tempresult = 0;
switch (str.charAt(0)) {
case '+':
tempresult = num1 + num2;
break;
case '-':
tempresult = num1 - num2;
break;
case '*':
tempresult = num1 * num2;
break;
case '/':
if(num2 == 0)
{
throw new Exception("出错:除数为 0");
}
tempresult = num1 / num2;
break;
case '%':
tempresult = num1 % num2;
break;
case '^':
tempresult = Math.pow(num1, num2);
break;
default:
throw new Exception("运算符: " + str + " 未识别!");
}
stack.push(tempresult);
} else {
stack.push(Double.valueOf(str));
}
}
return stack.pop();
}
public static void main(String[] args) { Scanner reader = new Scanner(System.in);
while(true)
{
String s = reader.nextLine();
double result = 0;
try {
result = Calculator2(s);
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
System.out.println(result);
}
}
}