AoC 2024, day 2, part 1 (dc)

# Command: dc -fdc-p1.dc <input

[q]  sQ
[0*] sZ
[1+] sC

0                               # sum = 0
[
    ? z d1=Q

    # stack: n r1 r2 ... rn sum
    2- dsn                      # i=n (number of diffs)
    [
        _3Rr d                  # copy r2; stack: r2 r2 r1 i ...
        3R- Sd                  # push diff on d stack; stack: r2 i r3 ...
        r1- d0<I                # i--
    ] dsIx *                    # end: 0*rn

    ld+ sa                      # a = dn + 0

    0 ln                        # i=n c=0
    [
        r Ldd d*v               # abs(di) di c i ...
        3<Z                     # top zeroed if >= 3
        la* 0<C                 # c++ if > 0
        r1- d0<I                # i--
    ] dsIx +                    # end: 0+c

    ln /+

    lMx
] dsMx

[Part 1: ]n rp