AoC 2025 day 9 part 1 (dc)

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

[sm0] sS                    # store top in S, replace with 0

1 ?                         # y x i=0
[
    3R1+                    # i++ y x
    d3R r:y                 # y(i) = y
    d3R r:x                 # x(i) = x
    ? z1<L
] dsLx

# stack: i=num
d;x r d;y
1:y r 1:x                   # add last to slot 1 (forms cycle)

r                           # i
[
    d1-                     # j=i-1 i
    [
        d;x r d;y           # y(j) j x(j) i
        4R
        d;x r d;y           # y(i) i x(i) y(j) j x(j)
        4R   -d*v1+         # abs(delta y)+1 i x(i) j x(j)
        5R4R -d*v1+ *       # area i j
        d lm<S s.

        r1- d0<J
    ] dsJx +
    1- d1<I
] dsIx

[Part 1: ]n lmp