Example from Computer Languages

A student working in DNA research had the task of finding repeated sequences of M values in a long sequence of values:

    ACTCGGATCTTGCATTTCGGCAATTGGACCCTGACTTGGCCA ...

Wrote the simplest (and therefore, most efficient?) program:

    DO 10 I = 1, N-M
    DO 10 J = I+1, N-M
    FOUND = .TRUE.
    DO 20 K = 1, M
20  IF X[I+K-1] .NE. X[J+K-1] THEN FOUND = .FALSE.
    IF FOUND THEN ...
10  CONTINUE

Took a depressingly long time.