全排列（递归）

/**
 *  1 2 2 3 4 5
 *  交换的方式
 */
public class Main
{
	static int count = 0;
	
    public static void main(String[] args)
	{
    	char[]arr = {'1','2','2','3','4','5'};
        dfs1(0,5,arr);
        System.out.println(count);
	}
    public static void dfs1(int start, int end, char[]arr) {
    	if (start == end) {
    		count++;
    		System.out.println(String.valueOf(arr));
    	}else {
    		for (int i = start; i <= end; i++) {
    			swap(start, i, arr);
    			dfs1(start+1, end, arr);
    			swap(start, i, arr);
    		}
    	}
    }
    public static void swap(int a, int b, char[]arr) {
    	char temp = arr[a];
    	arr[a] = arr[b];
    	arr[b] = temp;
    }
}

/**
 *  1 2 2 3 4 5     dfs深搜
 */
public class Test
{
	public static int count = 0;
	public static boolean[]flag = {false,false,false,false,false,false};
	public static char[]result;
	
    public static void main(String[] args)
	{
    	result = new char[6];
    	char[]arr = {'1','2','2','3','4','5'};
        dfs2(0,"",arr);
        System.out.println(count);
	}
    public static void dfs2(int index, String str, char[]arr) {
    	if (index == 6) {
    		System.out.println(String.valueOf(result));
    		count++;
    	}else {
	    	for (int i = 0; i < arr.length; i++) {
	    		if (flag[i] == false) {
	    			flag[i] = true;
	    			result[index] = arr[i];
	    			dfs2(index+1, str+arr[i], arr);
 	    			flag[i] = false;
	    		}
	    	}
    	}
    }
}