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这是一个四则混合运算程序,没什么做优化,也没做什么注释,(人啊,总喜欢偷懒的.)
这个版本我已经定为了2.21版本.呵呵.
从最先的1.0到2.0的改动很大.除了运算思想没动处,其它的都在2.0做了重新设计.
这种程序其实网上一大把（算法也好得多）。此仅为无聊找点事情做而已。
/**
*四则混合运算程序
*作者:黄剑武
*时间:2005年4月29日
*版本:2.21
*修改日志:2.0
* 1.更改表达式用户输入方式.
* 2.对用户输入的表达式进行有效性字符过滤.
* 3.使用double代替原int数值,并且使用严格浮点运算提高运算精度.
* 4.解除对运算数字只能是一位的限制.
* 5.优化了部分代码.
*修改日志:2.1
* 1.加入表达式括号匹配功能.
*修改日志:2.2
* 1.加入表达式处理功能.
*修改日志:2.21
* 1.修改部分语法以支持jdk1.5中的泛型用法.
*/
import java.lang.reflect.array;
import java.util.*;
import java.util.regex.*;
import java.lang.*;
import java.io.*;
//测试用例:1-3*(4-(2+5*3)+5)-6/(1+2)=23
//测试用例:11.2+3.1*(423-(2+5.7*3.4)+5.6)-6.4/(15.5+24)=1273.4199746835445
class calculator
{
public static void main(string[] args) throws ioexception
{
string str_input;
double f_output;
while (true)
{
system.out.print(“输入表达式: “);
system.out.flush();
str_input = getstring();
if (str_input.equals(“”))
{
break;
}
calculator calculator = new calculator();
//以下对输入字符串做规则处理
str_input = calculator.checkexpression(str_input);
if (str_input.equals(“”))
{
system.out.println(” 表达式出错 “);
}
//以下对输入字符串做表达式转换
vector<string> v_compute = calculator.getexpression(str_input);
/*
for (int i=0;i<v_compute.size();i++ )
{
system.out.println(” “+v_compute.get(i));
}
*/
//以下进行后缀表达式转换
vector<string> v_tmp_prefix = calculator.transformprefix(v_compute);
/*
for (int i=0;i<v_tmp_prefix.size();i++ )
{
system.out.println(v_tmp_prefix.get(i));
}
*/
//以下进行后缀表达式运算
f_output = calculator.evaluateprefix(v_tmp_prefix);
system.out.println(“结果 = ” + f_output);
}
}
/**
*静态方法,用来从控制台读入表达式
*/
public static string getstring() throws ioexception
{
inputstreamreader isr = new inputstreamreader(system.in);
bufferedreader br = new bufferedreader(isr);
string s = br.readline();
return s;
}
/**
*输入字符串转换.把从控制台读入的字符串转成表达式存在一个队列中.
*例:123+321 存为”123″”+””321″
*/
public vector<string> getexpression(string str)
{
vector<string> v_temp = new vector<string>();
char[] temp = new char[str.length()];
str.getchars(0,str.length(),temp,0);
string fi = “”;
int x=0,i=0;
string regex_fig = “[\\.\\d]”; //匹配数字和小数点
string regex_operator = “[\\+\\-\\*/\\(\\)]”; //匹配运算符(+,-,*,/)和括号(“(“,”)”)
pattern p_fig = pattern.compile(regex_fig);
pattern p_operator = pattern.compile(regex_operator);
matcher m = null;
boolean b;
while (i<str.length())
{
character c = new character(temp[i]);
string s = c.tostring();
//system.out.println(“char c = “+s);
m = p_operator.matcher(s);
b = m.matches();
if (b)
{
//system.out.println(“matches operator”);
v_temp.add(fi);
fi=””;
v_temp.add(s);
}
m = p_fig.matcher(s);
b = m.matches();
if (b)
{
//system.out.println(“matches fig”);
fi=fi+s;
}
i++;
}
v_temp.add(fi);
return v_temp;
}
/**
*转换中序表示式为前序表示式
*/
public vector<string> transformprefix(vector<string> v_expression)
{
vector<string> v_prefix = new vector<string>();
stack<string> s_tmp = new stack<string>();
string regex_float = “\\d+(\\.\\d+)?”; //匹配正浮点数
pattern p_float = pattern.compile(regex_float);
matcher m = null;
boolean b;
string str_elem = “”;
for (int i=0;i<v_expression.size();i++ )
{
str_elem = v_expression.get(i).tostring();
m = p_float.matcher(str_elem);
b = m.matches();
if (b)
{
v_prefix.add(str_elem);
}
if (str_elem.equals(“+”)||str_elem.equals(“-“))
{
if (s_tmp.isempty())
{
s_tmp.push(str_elem);
}
else
{
while(!s_tmp.isempty())
{
string str_tmp = s_tmp.peek();
if ( str_tmp.equals(“(“))
{
break;
}
else
{
v_prefix.add(s_tmp.pop());
}
}
s_tmp.push(str_elem);
}
}
if (str_elem.equals(“*”)||str_elem.equals(“/”))
{
if (s_tmp.isempty())
{
s_tmp.push(str_elem);
}
else
{
while(!s_tmp.isempty())
{
string str_tmp = s_tmp.peek();
if ( str_tmp.equals(“(“) || str_tmp.equals(“+”) || str_tmp.equals(“-“))
{
break;
}
else
{
v_prefix.add(s_tmp.pop());
}
}
s_tmp.push(str_elem);
}
}
if (str_elem.equals(“(“))
{
s_tmp.push(str_elem);
}
if (str_elem.equals(“)”))
{
while(!s_tmp.isempty())
{
string str_tmp = s_tmp.peek();
if (str_tmp.equals(“(“))
{
s_tmp.pop();
break;
}
else
{
v_prefix.add(s_tmp.pop());
}
}
}
}
while(!s_tmp.isempty())
{
v_prefix.add(s_tmp.pop());
}
return v_prefix;
}
/**
*前缀表示式求值
*/
public strictfp double evaluateprefix(vector<string> v_prefix)
{
string str_tmp = “”;
double num1,num2,interans = 0;
stack<double> s_compute = new stack<double>();
int i = 0;
while(i<v_prefix.size())
{
str_tmp = v_prefix.get(i).tostring();
if (!str_tmp.equals(“+”) && !str_tmp.equals(“-“) && !str_tmp.equals(“*”) && !str_tmp.equals(“/”))
{
interans = s_compute.push(double.parsedouble(str_tmp));
}
else
{
num2=(double)(s_compute.pop());
num1=(double)(s_compute.pop());
if (str_tmp.equals(“+”))
{
interans = num1+num2;
}
if (str_tmp.equals(“-“))
{
interans = num1-num2;
}
if (str_tmp.equals(“*”))
{
interans = num1*num2;
}
if (str_tmp.equals(“/”))
{
interans = num1/num2;
}
s_compute.push(interans);
}
i++;
}
return interans;
}
/**
*括号匹配检测
*/
public boolean checkbracket(string str)
{
stack<character> s_check = new stack<character>();
boolean b_flag = true;
for (int i=0;i<str.length();i++)
{
char ch = str.charat(i);
switch(ch)
{
case (:
s_check.push(ch);
break;
case ):
if (!s_check.isempty())
{
char chx = s_check.pop();
if (ch==) && chx!=()
{
b_flag = false;
}
} else {
b_flag = false;
}
break;
default:
break;
}
}
if (!s_check.isempty())
{
b_flag = false;
}
return b_flag;
}
/**
*表达式正确性规则处理与校验
*/
public string checkexpression(string str)
{
stack<character> s_check = new stack<character>();
stack<character> s_tmp = new stack<character>();
string str_result = “”;
string str_regex = “^[\\.\\d\\+\\-\\*/\\(\\)]+$“; //匹配合法的运算字符”数字,.,+,-,*,/,(,),”
pattern p_filtrate = pattern.compile(str_regex);
matcher m = p_filtrate.matcher(str);
boolean b_filtrate = m.matches();
if (!b_filtrate)
{
str_result = “”;
return str_result;
}
string str_err_float = “.*(\\.\\d*){2,}.*”; //匹配非法的浮点数.
pattern p_err_float = pattern.compile(str_err_float);
matcher m_err_float = p_err_float.matcher(str);
boolean b_err_float = m_err_float.matches();
if (b_err_float)
{
str_result = “”;
return str_result;
}
for (int i=0;i<str.length();i++)
{
char ch = str.charat(i);
if (checkfig(ch))
{
if (!s_tmp.isempty()&&s_tmp.peek()==))
{
str_result = “”;
return str_result;
}
s_tmp.push(ch);
str_result = str_result+ch;
}
switch(ch)
{
case (:
if (!s_tmp.isempty()&&s_tmp.peek()==.)
{
str_result = “”;
return str_result;
}
s_check.push(ch);
if (s_tmp.isempty()||(!this.checkfig(s_tmp.peek())&&s_tmp.peek()!=)))
{
str_result = str_result+ch;
} else {
str_result = str_result+”*”+ch;
}
s_tmp.push(ch);
break;
case ):
if (!s_check.isempty())
{
char chx = s_check.pop();
if (ch==) && chx!=()
{
str_result = “”;
return str_result;
}
} else {
str_result = “”;
return str_result;
}
if (s_tmp.peek()==.||(!this.checkfig(s_tmp.peek())&&s_tmp.peek()!=)))
{
str_result = “”;
return str_result;
}
s_tmp.push(ch);
str_result = str_result+ch;
break;
case +:
case -:
if (!s_tmp.isempty()&&(s_tmp.peek()==+||s_tmp.peek()==-||s_tmp.peek()==*||s_tmp.peek()==/||s_tmp.peek()==.))
{
str_result = “”;
return str_result;
}
if (s_tmp.isempty()||s_tmp.peek()==()
{
str_result = str_result+”0″+ch;
} else {
str_result = str_result+ch;
}
s_tmp.push(ch);
break;
case *:
case /:
if (s_tmp.isempty()||s_tmp.peek()==.||(!this.checkfig(s_tmp.peek())&&s_tmp.peek()!=)))
{
str_result = “”;
return str_result;
}
s_tmp.push(ch);
str_result = str_result+ch;
break;
case .:
if (s_tmp.isempty()||!this.checkfig(s_tmp.peek()))
{
str_result = str_result+”0″+ch;
} else {
str_result = str_result+ch;
}
s_tmp.push(ch);
break;
default:
break;
}
}
if (!s_check.isempty())
{
str_result = “”;
return str_result;
}
return str_result;
}
private static boolean checkfig(object ch)
{
string s = ch.tostring();
string str_regexfig = “\\d“; //匹配数字
pattern p_fig = pattern.compile(str_regexfig);
matcher m_fig = p_fig.matcher(s) ;
boolean b_fig = m_fig.matches();
return b_fig;
}
};
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