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