permutation.java

算法设计与分析 1. 用直接递归方法计算n！： （2）通过键盘输入n的值

/**
 * @(#)Permutation.java
 *
 *
 * @author 
 * @version 1.00 2008/10/22
 */
 package javaTest;
import java.util.Scanner;
import java.io.*;
import java.io.BufferedReader; 
import java.io.IOException; 
import java.io.InputStreamReader;
public class Permutation {
        
    /**
     * Creates a new instance of <code>Permutation</code>.
     */
     public static void swap(Object[]a,int i,int j)
     {
     	Object temp=a[i];
     	a[i]=a[j];
     	a[j]=temp;
     }
    public static void Permutation(Object[]list,int k,int m) {
    	if(k==m)
    	{for(int i=0;i<=m;i++)
    		System.out.print(list[i]);
    		System.out.println();
    	}
    	else
    		for(int i=k;i<=m;i++)
    		{
    			swap(list,k,i);
    			Permutation(list,k+1,m);
    			swap(list,k,i);
    		}
    }
    
    /**
     * @param args the command line arguments
     */
     public static void main(String[] args)  {
     	
     int n=0,m=0;
        Object list[];
        Scanner   scan=new  Scanner(System.in);
        System.out.print("input n=");
        n=scan.nextInt();
        list=new Object[n];	
     	
     	BufferedReader br=new BufferedReader(new InputStreamReader(System.in)); 
         
         
        for(int i=0;i<n;i++) 
       { 
       try { 
       System.out.print("请输入第"+(i+1)+"个数："); 
       list[i]=Integer.parseInt(br.readLine()); 
       } catch (IOException e) { 
       e.printStackTrace(); 
} 
} 

     	 
        
        Permutation(list,0,n-1); 
        	
     
     
    
}
}