Ancestors

Written by Russ Cox on 2024-12-02 at 15:34

Ivy remains a good choice for

[#]AdventOfCode.

Day 1:

sample = transp read "sample.txt"

op sort x = x[up x]

op solve x = +/abs (sort x[1]) - sort x[2]

solve sample

op solve2 x = +/x[1] * +/x[1] o.== x[2]

solve2 sample

https://adventofcode.com

(Ivy in 2021: https://www.youtube.com/playlist?list=PLrwpzH1_9ufMLOB6BAdzO08Qx-9jHGfGg)

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Written by Russ Cox on 2024-12-02 at 15:35

Day 2:

sample = read "sample.txt"

op delta x = (1 drop x) - -1 drop x

op safeInc x = &/ (delta x) in 1 2 3

op safeDec x = &/ (delta x) in -1 -2 -3

op safe x = (safeInc x) | safeDec x

op solve x = +/ safe@ x

solve sample

op i delete x = (i != iota rho x) sel x

op safe2 x = |/ safe@ (iota rho x) @delete x

op solve2 x = +/ safe2@ x

solve sample

(Using the non-standard map operator-modifier '@' that I added to my copy in 2021. https://github.com/rsc/ivy)

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Written by Russ Cox on 2024-12-03 at 06:31

Day 3 part 1.

The function 'c step s' steps the state machine state s to incorporate the new character c.

(step/ flip x) runs the state machine over the whole string, left to right.

The reduction base case for "...yz" is 'y' step 'z', which step rewrites to ('y' step 'z' step initial-state).

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Written by Russ Cox on 2024-12-03 at 06:32

Day 3 part 2.

The function 'c step2 s' is the updated state machine, with an extra value tracking whether mul(x,y) is enabled. step2 takes care of do()/don't() processing and invokes 'step' (from part 1) to handle mul(x,y) when appropriate.

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Toot

Written by Russ Cox on 2024-12-04 at 14:45

Day 4 part 1 https://adventofcode.com/2024/day/4 #AdventOfCode

pad dot-pads the matrix to avoid wraparound.

x y shift m rotates the matrix x left, y down.

d(=x y) shift4 m produces the 4 matrices shifted by d*0 1 2 3.

d XMAS m identifies the X in XMAS in direction d.

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Descendants

Written by Russ Cox on 2024-12-04 at 14:49

Day 4 part 2 #AdventOfCode

d shift3 m produces the 3 matrices shifted by d*-1 0 1.

d MAS m identifies the A in MAS in direction d.

d xMAS m identifies the A in MAS in direction d or -d.

xMAS m identifies the A in an X-MAS.

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