--第四关：跳马

declare @t table(p varchar(max),x int,y int)
insert into @t 
select 'p11',1,1 union 
select 'p12',1,2 union 
select 'p13',1,3 union 
select 'p14',1,4 union 
select 'p21',2,1 union 
select 'p22',2,2 union 
select 'p23',2,3 union 
select 'p24',2,4 union 
select 'p31',3,1 union 
select 'p32',3,2 union 
select 'p33',3,3 union 
select 'p34',3,4 union 
select 'p42',4,2 union 
select 'p43',4,3 

;with t(pstart,p,c,x,y) as
(
    select  p,p,1,x,y from @t
        union all
    select t.pstart,t.p+'->'+t_next.p,c+1,t_next.x,t_next.y from @t t_next,t where 
        (
            (abs(t_next.x-t.x)=1 and abs(t_next.y-t.y)=2) or
            (abs(t_next.x-t.x)=2 and abs(t_next.y-t.y)=1) )
            and (CHARINDEX(t_next.p,t.p)=0 or (c=14 and t_next.p=t.pstart))
)
select p from t  where c=15