instead of the printf loop
for(i=1;i<12;i++){if(!i%3)printf("\n");printf("%d",i);}
just use
for(i=1;i<12;i++) printf("%c%d",!(i%3)*10,i);
it helps me so much .
@SamHocevar 's answer (shorter by 2bytes)
for(i=1;i<12;i++) printf("\n%d"+!!(i%3),i);
Credits to @AbhayAravinda for ripping off three more bytes
for(i=1;i++<12;) printf("\n%d"+!!(i%3),i);
The incrementer here works as a part of the inspector.