The gravity assist was successful, and you're well on your way to the Venus refuelling station. During the rush back on Earth, the fuel management system wasn't completely installed, so that's next on the priority list.

Opening the front panel reveals a jumble of wires. Specifically, two wires are connected to a central port and extend outward on a grid. You trace the path each wire takes as it leaves the central port, one wire per line of text (your puzzle input).

Read the full puzzle.

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

namespace AdventOfCode.Y2019.Day03;

[ProblemName("Crossed Wires")]
class Solution : Solver {

    public object PartOne(string input) => Solve(input, (x) => Math.Abs(x.irow) + Math.Abs(x.icol));

    public object PartTwo(string input) => Solve(input, (x) => x.distance1 + x.distance2);

    int Solve(string input, Func<(int irow, int icol, int distance1, int distance2), int> distance) {
        var paths = input.Split("\n");
        var trace1 = Trace(paths[0]);
        var trace2 = Trace(paths[1]);

        var distances =
            from pos in trace1.Keys
            where trace2.ContainsKey(pos)
            select distance((pos.irow, pos.icol, trace1[pos], trace2[pos]));
        return distances.Min();
    }

    Dictionary<(int irow, int icol), int> Trace(string path) {
        var res = new Dictionary<(int irow, int icol), int>();

        var (irow, icol, distance) = (0, 0, 0);
        foreach (var step in path.Split(",")) {
            var (drow, dcol) = step[0] switch {
                'U' => (-1, 0),
                'D' => (1, 0),
                'R' => (0, -1),
                'L' => (0, 1),
                _ => throw new ArgumentException()
            };

            for (var i = 0; i < int.Parse(step.Substring(1)); i++) {
                (irow, icol, distance) = (irow + drow, icol + dcol, distance + 1);

                if (!res.ContainsKey((irow, icol))) {
                    res[(irow, icol)] = distance;
                }
            }
        }

        return res;
    }
}

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