It's finally time to meet back up with the Elves. When you try to contact them, however, you get no reply. Perhaps you're out of range?

You know they're headed to the grove where the star fruit grows, so if you can figure out where that is, you should be able to meet back up with them.

Read the full puzzle.

using System.Linq;
using System.Collections.Generic;

namespace AdventOfCode.Y2022.Day20;

[ProblemName("Grove Positioning System")]
class Solution : Solver {

    record Data(int idx, long num);

    public object PartOne(string input) =>
         GetGrooveCoordinates(Mix(Parse(input, 1)));

    public object PartTwo(string input) {
        var data = Parse(input, 811589153L);
        for (var i = 0; i < 10; i++) {
            data = Mix(data);
        }
        return GetGrooveCoordinates(data);
    }

    List<Data> Parse(string input, long m) =>
        input
            .Split("\n")
            .Select((line, idx) => new Data(idx, long.Parse(line) * m))
            .ToList();

    List<Data> Mix(List<Data> numsWithIdx) {
        var mod = numsWithIdx.Count - 1;
        for (var idx = 0; idx < numsWithIdx.Count; idx++) {
            var srcIdx = numsWithIdx.FindIndex(x => x.idx == idx);
            var num = numsWithIdx[srcIdx];

            var dstIdx = (srcIdx + num.num) % mod;
            if (dstIdx < 0) {
                dstIdx += mod;
            }

            numsWithIdx.RemoveAt(srcIdx);
            numsWithIdx.Insert((int)dstIdx, num);
        }
        return numsWithIdx;
    }

    long GetGrooveCoordinates(List<Data> numsWithIdx) {
        var idx = numsWithIdx.FindIndex(x => x.num == 0);
        return (
            numsWithIdx[(idx + 1000) % numsWithIdx.Count].num +
            numsWithIdx[(idx + 2000) % numsWithIdx.Count].num +
            numsWithIdx[(idx + 3000) % numsWithIdx.Count].num
        );
    }
}

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