后缀表达式字符串计算 --只对个位数计算及 1* 2 -3+6/2

Java数据结构和算法中文第二版.pdf 代码

StackX.java

package com.ch4.postfix;

public class StackX {

private int maxSize ;
private int[] stackArray ;
private int top ;

public StackX(int size){

maxSize = size ;
stackArray = new int[size] ;
top = -1 ;
}

public void push(int elem){

stackArray[++top] = elem ;
}

public int pop(){

return stackArray[top--] ;
}

public int peek(){

return stackArray[top] ;
}

public boolean isEmpty(){

return (top == -1) ;
}

public int peekIndex(int index){

return stackArray[index] ;
}

public int size(){

return top +1 ;
}
public void displayStack(String info){

System.out.print(info) ;
System.out.print("Stack (bottom -->top): ") ;
for (int j = 0; j < size(); j++){
System.out.print(peekIndex(j)) ;
System.out.print(' ');
}
System.out.println() ;
}
}

Postfix.java

package com.ch4.postfix;

public class Postfix {
private StackX theStack ;
private String input ;

public Postfix(String S){
input = S ;
}

public int doParse(){

theStack = new StackX(20) ;
char ch ;
int i ;
int num1 , num2 ,interAns ;

for (i = 0; i < input.length(); i++){
ch = input.charAt(i) ;

theStack.displayStack("" + ch + "") ;

if ((ch >= '0') && (ch <='9')){
theStack.push((int)(ch -'0')) ;
}else{
num2 = theStack.pop() ;
num1 = theStack.pop() ;
switch(ch){
case '+' :
interAns = num1 + num2 ;
break ;
case '-' :
interAns = num1 - num2 ;
break ;
case '*' :
interAns = num1 * num2 ;
break ;
case '/' :
interAns = num1 / num2 ;
break ;
default:
interAns = 0;
break ;
}
theStack.push(interAns) ;
}
}

interAns = theStack.pop() ;
return interAns ;
}
}

PostfixApp.java

package com.ch4.test;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

import com.ch4.infix.Infix;
import com.ch4.postfix.Postfix;

public class PostfixApp {

/**
* @param args
*/
public static void main(String[] args)  throws IOException{
String input , output ;

while(true ){

System.out.print("Enter infix: ") ;
System.out.flush() ;
input = getString() ;

if (input.equals("")){
break ;
}
Infix theTrans = new Infix(input) ;

output = theTrans.doTrans() ;

Postfix postfix = new Postfix(output) ;
System.out.println("src String : " + input) ;
System.out.println("post src String : " + output) ;
System.out.println("Postfix is :" + postfix.doParse()) ; ;
}
}

public static String getString() throws IOException{

InputStreamReader isr = new InputStreamReader(System.in) ;
BufferedReader br = new BufferedReader(isr) ;
String s = br.readLine() ;
return s ;

}

}

只对个位数计算，如 ：1* 2 -3+6/2

运行结果：

Enter infix: 1 + 2*3 + (9-5) /2

For 1 Stack (bottom -->top):

For + Stack (bottom -->top):

For 2 Stack (bottom -->top): +

For * Stack (bottom -->top): +

For 3 Stack (bottom -->top): + *

For + Stack (bottom -->top): + *

For ( Stack (bottom -->top): +

For 9 Stack (bottom -->top): + (

For - Stack (bottom -->top): + (

For 5 Stack (bottom -->top): + ( -

For ) Stack (bottom -->top): + ( -

For / Stack (bottom -->top): +

For 2 Stack (bottom -->top): + /

While Stack (bottom -->top): + /

While Stack (bottom -->top): +

End Stack (bottom -->top):

src String : 1 + 2*3 + (9-5) /2

post src String : 123*+95-2/+

1Stack (bottom -->top):

2Stack (bottom -->top): 1

3Stack (bottom -->top): 1 2

*Stack (bottom -->top): 1 2 3

+Stack (bottom -->top): 1 6

9Stack (bottom -->top): 7

5Stack (bottom -->top): 7 9

-Stack (bottom -->top): 7 9 5

2Stack (bottom -->top): 7 4

/Stack (bottom -->top): 7 4 2

+Stack (bottom -->top): 7 2

Postfix is :9