The device on your wrist beeps several times, and once again you feel like you're falling.

"Situation critical," the device announces. "Destination indeterminate. Chronal interference detected. Please specify new target coordinates."

Read the full puzzle.

using System;
using System.Linq;

namespace AdventOfCode.Y2018.Day06;

[ProblemName("Chronal Coordinates")]
class Solution : Solver {

    public object PartOne(string input) {
        var coords = Parse(input);

        var minX = coords.Min(coord => coord.x) - 1;
        var maxX = coords.Max(coord => coord.x) + 1;
        var minY = coords.Min(coord => coord.y) - 1;
        var maxY = coords.Max(coord => coord.y) + 1;

        var area = new int[coords.Length];

        foreach (var x in Enumerable.Range(minX, maxX - minX + 1)) {
            foreach (var y in Enumerable.Range(minY, maxY - minX + 1)) {
                var d = coords.Select(coord => Dist((x, y), coord)).Min();
                var closest = Enumerable.Range(0, coords.Length).Where(i => Dist((x, y), coords[i]) == d).ToArray();

                if (closest.Length != 1) {
                    continue;
                }

                if (x == minX || x == maxX || y == minY || y == maxY) {
                    foreach (var icoord in closest) {
                        if (area[icoord] != -1) {
                            area[icoord] = -1;
                        }
                    }
                } else {
                    foreach (var icoord in closest) {
                        if (area[icoord] != -1) {
                            area[icoord]++;
                        }
                    }
                }
            }
        }
        return area.Max();
    }

    public object PartTwo(string input) {
        var coords = Parse(input);

        var minX = coords.Min(coord => coord.x) - 1;
        var maxX = coords.Max(coord => coord.x) + 1;
        var minY = coords.Min(coord => coord.y) - 1;
        var maxY = coords.Max(coord => coord.y) + 1;

        var area = 0;

        foreach (var x in Enumerable.Range(minX, maxX - minX + 1)) {
            foreach (var y in Enumerable.Range(minY, maxY - minX + 1)) {
                var d = coords.Select(coord => Dist((x, y), coord)).Sum();
                if (d < 10000)
                    area++;
            }
        }
        return area;
    }

    int Dist((int x, int y) c1, (int x, int y) c2) {
        return Math.Abs(c1.x - c2.x) + Math.Abs(c1.y - c2.y);
    }

    (int x, int y)[] Parse(string input) => (
            from line in input.Split("\n")
            let coords = line.Split(", ").Select(int.Parse).ToArray()
            select (coords[0], coords[1])
        ).ToArray();
}

Please ☆ my repo if you like it!