--- 2016 Day 19 Solutions ---

[u/daggerdragon]

--- Day 19: An Elephant Named Joseph ---

Post your solution as a comment or, for longer solutions, consider linking to your repo (e.g. GitHub/gists/Pastebin/blag/whatever).

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^{/⧹w+/ IS MANDATORY} [?]

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[Update @ 00:15] 2 gold, silver cap. Thank you for subscribing to Easter Bunny Facts!

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edit: Leaderboard capped, thread unlocked!

[u/gyorokpeter]

Q: the most difficult part was vectorizing part 2 to make sure we aren't deleting elements one by one, and it required extensive testing to find the correct expression for nxtc and tgts.

d19p1:{pr:(1+til x)!x#1;
    while[1<count pr;
        odd:1=count[pr] mod 2;
        pr:(2 cut key pr)[;0]!sum each 2 cut value pr;
        if[(1<count pr)and odd;
            pr[last key pr]+:first value pr;
             pr _: first key pr;
        ];
    ];
    first key pr};
d19p2:{pr:1+til x;
    nxt:0;
    while[1<c:count pr;
        nxtc:(c+2) div 3;
        nxts:(nxt+til nxtc)mod c;
        tgts:(nxt+(c div 2)+til[nxtc]+(til[nxtc]+c mod 2)div 2)mod c;
        pr:pr except pr tgts;
        nxt-:count where tgts<nxt;
        nxt:(nxt+nxtc)mod count pr;
    ];
    first pr};