Create Flags for Consecutive and Non Consecutive Flags

[Paakay]

Hello All,  I want to flag ID's with consecutive flags as 1 and those without consecutive flags as 0. For example ID 1 is consecutive because it starts from cycle 1 to cycle 4 so I create a flag for ID 1 as 1. However for ID's with no consecutive cycle numbers like ID 2 (its starts from cycle 2 to cycle 5, missing cycle 1) and ID 3 also starts from cycle 8 missing cycles 1-7,  I flags these ID's as 0. Is there a way to go about this. Thank you.

Data have;
 input ID $1. Cycle;
Datalines;
1    1
1    1
1    2
1    3
1    4
2   3
2   4
2   5
3   8
3   8
;
run; 

[Kurt_Bremser]

Run a DO loop:

data want;
flag = 1;
cy = -1;
do until (last.id);
  set have;
  by id;
  if cycle gt cy + 1 then flag = 0;
  cy = cycle;
end;
keep id flag;
run;

(untested, posted from my tablet)

If you want to "remerge" the flag to the original dataset, add a second DO loop that reads the same group and OUTPUTs.