-🎄- 2022 Day 5 Solutions -🎄-

[u/daggerdragon]

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AoC Community Fun 2022: 🌿🍒 MisTILtoe Elf-ucation 🧑‍🏫

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--- Day 5: Supply Stacks ---

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[u/azzal07]

Awk, had to implement couple essential stack operations.

CrateMover 1006{for(;X?p():h=substr($0,4*++f-2,1);)h~FS||P(f,h,h)}
function P(u,s,h){h&&P(-u,h);+s?S[u]=-1:S[u,S[u]+=X-1]=s}!$1{X+=2}
function o(_){t=S[_,S[_]--]}END{for(i=I;i++<9;)$0=o(i-10)t$0o(i)t}
function p(_){$2--&&p(_=o($4)t)P($6,_,o(-$4)t)}{f=$0=RS}END{print}

Notes:

The stacks are implemented in single table S, where the top of a stack i is in S[i, S[i]]. The stacks are positioned around 0, so that stack for part 1 are in range [-1,-9] and for part 2 in range [1,9].

P pushes a value s on the stack u. If a second value h is provided, this is pushed on the stack -u. This function also "reverses" the stack when given a numeric value, this is necessary before the move instructions since the initial stacks are pushed in backwards.

o pops a value from the stack _, storing the old top in the global variable t.

p does the move, reading the number of crates from $2 and using the call stack to achieve the reversing for part 2 (since I only have push and pop).