//检查当前状态   a为行 b为列 s为步数
void check(int a,int b,int s)
{
        //判断 最后一步
        if(s==16)
        {
                //越界与重步的判断
                if(a>=0&&b>=0&&a<4&&b<4&&qipan[a][b]==0)
                {
                        qipan[a][b]=s;
                }
                //如果越界重步 返回
                else return ;
        }

        
        
        //越界与重步的判断
        else if(a>=0&&b>=0&&a<4&&b<4&&qipan[a][b]==0)
        {
                qipan[a][b]=s;
                //检查下一个状态
                check(a+1,b+2,s+1);
                check(a-1,b+2,s+1);
                check(a+1,b-2,s+1);
                check(a-1,b-2,s+1);
                check(a+2,b+1,s+1);
                check(a+2,b-1,s+1);
                check(a-2,b+1,s+1);
                check(a-2,b-1,s+1);
                //如果八个方向都不行 清空状态 返回上一层
                qipan[a][b]=0;
                return ;
        }
        


        //如果越界重步 返回
        else return ;

}