java之全排列

如下面代码：

 

import java.util.ArrayList;

public class FullSort 
{
	public static void main(String[] args) 
	{
		String str = "2468";
		
		FullSort fs = new FullSort();
		
		ArrayList<String> list = fs.permutation(str);
		
		System.out.println("Total num : " + list.size());
		for(String s : list)
			System.out.println(s);
		
		System.out.println();
		
		int[] arr = {1, 2, 3, 4};
		fs.perm(arr, 0, arr.length-1);
	}

	public ArrayList<String> permutation(String str)
	{
		ArrayList<String> list = new ArrayList<String>();
		
		if(str.length() == 1) 
		{
			list.add(str);
		} 
		else 
		{
			String temp = "";
			String left = "";
			
			for(int i=0; i<str.length(); i++) 
			{
				temp = str.charAt(i) + "";
				left = str.substring(0, i) + str.substring(i+1);
				
				for(String element : permutation(left))
				{
					list.add(temp + element);
				}
			}
		}
		
		return list;
	}
	
	public void perm(int[] arr, int k, int m)
	{
		if(k == m)
		{
			for(int i=0; i<=m; i++)
			{
				System.out.print(arr[i]);
			}
			
			System.out.println();
		}
		else
		{
			for(int i=k; i<=m; i++)
			{
				Swap(arr, k, i);
				perm(arr, k+1, m);
				Swap(arr, k, i);
			}
		}
	}
	
	public void Swap(int[] arr, int i, int j)
	{
		int temp = -1;
		temp = arr[i];
		arr[i] = arr[j];
		arr[j] = temp;
	}
}

 

 

输出结果就不显示了。

 

如下面代码：

 

import java.util.ArrayList;
import java.util.LinkedList;
import java.util.List;

public class FullSort2 
{
	public static void main(String[] args) 
	{
		int[] arr = {1, 3, 5, 7};
		StringBuffer sb = new StringBuffer();
		ArrayList<Integer> list = new ArrayList<Integer>();
		
		for (int i=0; i<arr.length; i++) 
		{
			sb.append(arr[i]);
			list.add(arr[i]);
		}
		
		FullSort2 test = new FullSort2();
		
		test.printAll(sb, "", list.size());
		System.out.println();
		test.printAll(list, "", list.size());
	}
	
	public void printAll(StringBuffer candidate, String prefix, int length) 
	{
		if(prefix.length() == length)
		{
			System.out.println(prefix);
		}
		
		for(int i=0; i<candidate.length(); i++) 
		{
			StringBuffer temp = new StringBuffer(candidate.toString());
			String str = prefix+temp.charAt(i);
			temp.deleteCharAt(i);
			printAll(temp, str, length);
		}
	}
	
	public void printAll(List<Integer> candidate, String prefix, int length) 
	{
		if(prefix.length() == length)
		{
			System.out.println(prefix);
		}
		
		for(int i=0; i<candidate.size(); i++) 
		{
			List<Integer> temp = new LinkedList<Integer>(candidate);
			String str = prefix+temp.remove(i);
			printAll(temp, str, length);
		}
	}
}

 

结果也不输出了。