LeetCode/cs/map-of-highest-peak.cs

using Coord = (int x, int y);

public class Solution {
    private static readonly int UNSET = -1;
    private static readonly Coord[] DIRECTIONS = [
        (0, 1),
        (0, -1),
        (1, 0),
        (-1, 0)
    ];

    private static bool IsValid(Coord dimensions, Coord position) {
        var (width, height) = dimensions;
        var (x, y) = position;

        return y >= 0 && y < height && x >= 0 && x < width;
    }

    public int[][] HighestPeak(int[][] isWater) {
        var (width, height) = (isWater[0].Length, isWater.Length);
        var map = new int[height][];
        for (var y = 0; y < height; ++y) {
            map[y] = new int[width];
            Array.Fill(map[y], UNSET);
        }

        var q = new Queue<Coord>();
        for (var y = 0; y < height; ++y) {
            for (var x = 0; x < width; ++x) {
                if (isWater[y][x] != 1) {
                    continue;
                }

                q.Enqueue((x, y));
                map[y][x] = 0;
            }
        }

        var nextHeight = 1;
        for (var n = q.Count; n > 0; ++nextHeight, n = q.Count) {
            for (var i = 0; i < n; ++i) {
                var (x, y) = q.Dequeue();

                foreach (var (dx, dy) in DIRECTIONS) {
                    var nx = x + dx;
                    var ny = y + dy;
                    if (!IsValid((width, height), (nx, ny)) || map[ny][nx] != -1) {
                        continue;
                    }

                    map[ny][nx] = nextHeight;
                    q.Enqueue((nx, ny));
                }
            }
        }

        return map;
    }
}