程序代码：

#include <stdio.h>

static int path[6];
static int data[6]={1,2,2,3,4,5};
int count;
bool IsSafe(int pos,int index)      
{
    if( pos == 2 && data[index] == 4)
        return false;
    if(pos > 0 && data[path[pos-1]] == 3 && data[index] == 5)
        return false;
    if(pos > 0 && data[path[pos-1]] == 5 && data[index] == 3)
        return false;
    for( int i = 0; i < pos; i++)
        if( path[i] == index)
            return false;
    if(index == 1)
        for( int i=0; i < pos; i++)
            if( path[i] == 2)
                return false;
    return true;
}

void print()
{
    count++;
    for( int i = 0; i != 6; ++i)
        printf("%d",data[path[i]]);
    printf("\t");
}
void trial(int pos)
{
    if (pos >= 6)
        print();
    else for(int i=0; i<6;i++)
            {              
                if(IsSafe(pos,i))
                {
                    path[pos]=i;
                    trial(pos+1);
                }
            }
}

int main()
{
    trial(0);
    printf("\ntotal counts:%d\n",count);
    return 0;
}