With the Elves well on their way constructing the North Pole base, you turn your attention back to understanding the inner workings of programming the device.

You can't help but notice that the device's opcodes don't contain any flow control like jump instructions. The device's manual goes on to explain:

Read the full puzzle.

using System;
using System.Linq;

namespace AdventOfCode.Y2018.Day19;

[ProblemName("Go With The Flow")]
class Solution : Solver {

    public object PartOne(string input) {
        var ip = 0;
        var ipReg = int.Parse(input.Split("\n").First().Substring("#ip ".Length));
        var prg = input.Split("\n").Skip(1).ToArray();
        var regs = new int[6];
        while (ip >= 0 && ip < prg.Length) {
            var args = prg[ip].Split(" ");
            regs[ipReg] = ip;
            regs = Step(regs, args[0], args.Skip(1).Select(int.Parse).ToArray());
            ip = regs[ipReg];
            ip++;
        }
        return regs[0];
    }

    public object PartTwo(string input) {
        var t = 10551292;
        var r0 = 0;
        for (var x = 1; x <= t; x++) {
            if (t % x == 0)
                r0 += x;
        }
        return r0;
    }

    int[] Step(int[] regs, string op, int[] stm) {
        regs = regs.ToArray();
        regs[stm[2]] = op switch {
            "addr" => regs[stm[0]] + regs[stm[1]],
            "addi" => regs[stm[0]] + stm[1],
            "mulr" => regs[stm[0]] * regs[stm[1]],
            "muli" => regs[stm[0]] * stm[1],
            "banr" => regs[stm[0]] & regs[stm[1]],
            "bani" => regs[stm[0]] & stm[1],
            "borr" => regs[stm[0]] | regs[stm[1]],
            "bori" => regs[stm[0]] | stm[1],
            "setr" => regs[stm[0]],
            "seti" => stm[0],
            "gtir" => stm[0] > regs[stm[1]] ? 1 : 0,
            "gtri" => regs[stm[0]] > stm[1] ? 1 : 0,
            "gtrr" => regs[stm[0]] > regs[stm[1]] ? 1 : 0,
            "eqir" => stm[0] == regs[stm[1]] ? 1 : 0,
            "eqri" => regs[stm[0]] == stm[1] ? 1 : 0,
            "eqrr" => regs[stm[0]] == regs[stm[1]] ? 1 : 0,
            _ => throw new ArgumentException()
        };
        return regs;
    }
}

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