AoC 2025 day 4 part 1 (dc)

# Command: tr '.@' '12' <input | dc -fdc-p1.dc

# line x y -> line x y
[
    _3R
    r dF0* 3R d3R+      # roll=150*y+x x y line
    d Sr 1 r:g          # push roll on r; grid(roll) = 1
    3R
] s@

[1+] sP

0 Sr                    # Register stack r sentinel

2 ?                     # line y=2
[
    0 r                 # line x=0 y
    [
        A~              # chr line x y
        2=@             # record @ (2); line x y
        r1+r            # line x++ y
        d0<X
    ] dsXx *+

    1+                  # y++
    ? z1<Y
] dsYx 0*

[ ;g 3R+r ] s+

Lr                      # roll part1
[
    0r                  # roll count part1
    d F1+ l+x
    d F0+ l+x
    d E9+ l+x
    d  1+ l+x
    d  1- l+x
    d E9- l+x
    d F0- l+x
      F1- ;g   +        # count part1

    4>P                 # part1++ if (count < 4)

    Lr d0<L
] dsLx

[Part 1: ]n 3Rp