/ valid sudoko

i:,/i{(x;y)}\:/:i:(0 1 2;3 4 5;6 7 8)
n:1+!9

v:{(&/a _lin n)&a~?a:_dv[x]0}
r:&/v'
c:r@+:
k:{&/(v@,/)',/x ./:i}
f:{&/(r;c;k)@\:x}

m:(5 3 0 0 7 0 0 0 0
   6 0 0 1 9 5 0 0 0
   0 9 8 0 0 0 0 6 0
   8 0 0 0 6 0 0 0 3
   4 0 0 8 0 3 0 0 1
   7 0 0 0 2 0 0 0 6
   0 6 0 0 0 0 2 8 0
   0 0 0 4 1 9 0 0 5
   0 0 0 0 8 0 0 7 9)

1~f m

m:(8 3 0 0 7 0 0 0 0
   6 0 0 1 9 5 0 0 0
   0 9 8 0 0 0 0 6 0
   8 0 0 0 6 0 0 0 3
   4 0 0 8 0 3 0 0 1
   7 0 0 0 2 0 0 0 6
   0 6 0 0 0 0 2 8 0
   0 0 0 4 1 9 0 0 5
   0 0 0 0 8 0 0 7 9)

0~f m