Problem:
Score : 400 points

Problem Statement

A maze is composed of a grid of H \times W squares - H vertical, W horizontal.

The square at the i-th row from the top and the j-th column from the left - (i,j) - is a wall if S_{ij} is # and a road if S_{ij} is ..

There is a magician in (C_h,C_w). He can do the following two kinds of moves:

Move A: Walk to a road square that is vertically or horizontally adjacent to the square he is currently in.

Move B: Use magic to warp himself to a road square in the 5\times 5 area centered at the square he is currently in.

In either case, he cannot go out of the maze.

At least how many times does he need to use the magic to reach (D_h, D_w)?

Constraints

1 \leq H,W \leq 10^3

1 \leq C_h,D_h \leq H

1 \leq C_w,D_w \leq W

S_{ij} is # or ..

S_{C_h C_w} and S_{D_h D_w} are ..

(C_h,C_w) \neq (D_h,D_w)

Input

Input is given from Standard Input in the following format:

H W
C_h C_w
D_h D_w
S_{11}\ldots S_{1W}
\vdots
S_{H1}\ldots S_{HW}

Output

Print the minimum number of times the magician needs to use the magic. If he cannot reach (D_h,D_w), print -1 instead.

Sample Input 1

4 4
1 1
4 4
..#.
..#.
.#..
.#..

Sample Output 1

1

For example, by walking to (2,2) and then using the magic to travel to (4,4), just one use of magic is enough.

Note that he cannot walk diagonally.

Sample Input 2

4 4
1 4
4 1
.##.
####
####
.##.

Sample Output 2

-1

He cannot move from there.

Sample Input 3

4 4
2 2
3 3
....
....
....
....

Sample Output 3

0

No use of magic is needed.

Sample Input 4

4 5
1 2
2 5
#.###
####.
#..##
#..##

Sample Output 4

2

Solution in C# (.NET Core 3.1.201) (judge verdict: Accepted)

#region いつもの
using AtCoderProject;
using System;
using System.Collections.Generic;
using System.Linq;
using static AtCoderProject.Global;
using BigInteger = System.Numerics.BigInteger;
using BitOperations = System.Numerics.BitOperations;
using IEnumerable = System.Collections.IEnumerable;
using IEnumerator = System.Collections.IEnumerator;
using StringBuilder = System.Text.StringBuilder;
using Unsafe = System.Runtime.CompilerServices.Unsafe;

namespace AtCoderProject { using System.IO; using System.Text; using System.Diagnostics; using System.Runtime.CompilerServices; using System.Linq.Expressions; public static class Global { public static T[] NewArray<T>(int len0, T value) => new T[len0].Fill(value); public static T[] NewArray<T>(int len0, Func<T> factory) { var arr = new T[len0]; for (int i = 0; i < arr.Length; i++) arr[i] = factory(); return arr; } public static T[][] NewArray<T>(int len0, int len1, T value) where T : struct { var arr = new T[len0][]; for (int i = 0; i < arr.Length; i++) arr[i] = NewArray(len1, value); return arr; } public static T[][] NewArray<T>(int len0, int len1, Func<T> factory) { var arr = new T[len0][]; for (int i = 0; i < arr.Length; i++) arr[i] = NewArray(len1, factory); return arr; } public static T[][][] NewArray<T>(int len0, int len1, int len2, T value) where T : struct { var arr = new T[len0][][]; for (int i = 0; i < arr.Length; i++) arr[i] = NewArray(len1, len2, value); return arr; } public static T[][][] NewArray<T>(int len0, int len1, int len2, Func<T> factory) { var arr = new T[len0][][]; for (int i = 0; i < arr.Length; i++) arr[i] = NewArray(len1, len2, factory); return arr; } public static T[][][][] NewArray<T>(int len0, int len1, int len2, int len3, T value) where T : struct { var arr = new T[len0][][][]; for (int i = 0; i < arr.Length; i++) arr[i] = NewArray(len1, len2, len3, value); return arr; } public static T[][][][] NewArray<T>(int len0, int len1, int len2, int len3, Func<T> factory) { var arr = new T[len0][][][]; for (int i = 0; i < arr.Length; i++) arr[i] = NewArray(len1, len2, len3, factory); return arr; } public static long Pow(long x, int y) { long res = 1; for (; y > 0; y >>= 1) { if ((y & 1) == 1) res *= x; x *= x; } return res; } public static BigInteger ParseBigInteger(ReadOnlySpan<char> s) { /* 自前実装の方が速い */ BigInteger res; if (s.Length % 9 == 0) res = 0; else { res = new BigInteger(int.Parse(s.Slice(0, s.Length % 9))); s = s.Slice(s.Length % 9); } while (s.Length > 0) { var sp = s.Slice(0, 9); res *= 1000_000_000; res += int.Parse(sp); s = s.Slice(9); } return res; } public static int PopCount(int x) => BitOperations.PopCount((uint)x); public static int PopCount(long x) => BitOperations.PopCount((ulong)x); public static int PopCount(ulong x) => BitOperations.PopCount(x); public static int MSB(int x) => BitOperations.Log2((uint)x); public static int MSB(uint x) => BitOperations.Log2(x); public static int MSB(long x) => BitOperations.Log2((ulong)x); public static int MSB(ulong x) => BitOperations.Log2(x); public static int LSB(int x) => BitOperations.TrailingZeroCount((uint)x); public static int LSB(uint x) => BitOperations.TrailingZeroCount(x); public static int LSB(long x) => BitOperations.TrailingZeroCount((ulong)x); public static int LSB(ulong x) => BitOperations.TrailingZeroCount(x); } public static class Ext { public static bool UpdateMax<T>(this ref T r, T val) where T : struct, IComparable<T> { if (r.CompareTo(val) < 0) { r = val; return true; } return false; } public static bool UpdateMin<T>(this ref T r, T val) where T : struct, IComparable<T> { if (r.CompareTo(val) > 0) { r = val; return true; } return false; } public static long ToLong(this int i) => i; public static T[] Fill<T>(this T[] arr, T value) { Array.Fill(arr, value); return arr; } public static T[] Sort<T>(this T[] arr) { Array.Sort(arr); return arr; } public static string[] Sort(this string[] arr) => Sort(arr, StringComparer.OrdinalIgnoreCase); public static T[] Sort<T, U>(this T[] arr, Expression<Func<T, U>> selector) where U : IComparable<U> => Sort(arr, ExComparer<T>.CreateExp(selector)); public static T[] Sort<T>(this T[] arr, Comparison<T> comparison) { Array.Sort(arr, comparison); return arr; } public static T[] Sort<T>(this T[] arr, IComparer<T> comparer) { Array.Sort(arr, comparer); return arr; } public static T[] Reverse<T>(this T[] arr) { Array.Reverse(arr); return arr; } public static (int index, T max) MaxBy<T>(this T[] arr) where T : IComparable<T> { T max = arr[0]; int maxIndex = 0; for (int i = 0; i < arr.Length; i++) { if (max.CompareTo(arr[i]) < 0) { max = arr[i]; maxIndex = i; } } return (maxIndex, max); } public static (TSource item, TMax max) MaxBy<TSource, TMax>(this IEnumerable<TSource> source, Func<TSource, TMax> maxBySelector) where TMax : IComparable<TMax> { TMax max; TSource maxByItem; var e = source.GetEnumerator(); e.MoveNext(); maxByItem = e.Current; max = maxBySelector(maxByItem); while (e.MoveNext()) { var item = e.Current; var next = maxBySelector(item); if (max.CompareTo(next) < 0) { max = next; maxByItem = item; } } return (maxByItem, max); } public static (int index, T min) MinBy<T>(this T[] arr) where T : IComparable<T> { T min = arr[0]; int minIndex = 0; for (int i = 0; i < arr.Length; i++) { if (min.CompareTo(arr[i]) > 0) { min = arr[i]; minIndex = i; } } return (minIndex, min); } public static (TSource item, TMin min) MinBy<TSource, TMin>(this IEnumerable<TSource> source, Func<TSource, TMin> minBySelector) where TMin : IComparable<TMin> { TMin min; TSource minByItem; var e = source.GetEnumerator(); e.MoveNext(); minByItem = e.Current; min = minBySelector(minByItem); while (e.MoveNext()) { var item = e.Current; var next = minBySelector(item); if (min.CompareTo(next) > 0) { min = next; minByItem = item; } } return (minByItem, min); } public static IComparer<T> Reverse<T>(this IComparer<T> comparer) => Comparer<T>.Create((x, y) => comparer.Compare(y, x)); public static Dictionary<TKey, int> GroupCount<TSource, TKey>(this IEnumerable<TSource> source, Func<TSource, TKey> keySelector) => source.GroupBy(keySelector).ToDictionary(g => g.Key, g => g.Count()); public static Dictionary<TKey, int> GroupCount<TKey>(this IEnumerable<TKey> source) => source.GroupCount(i => i); public static Span<T> AsSpan<T>(this List<T> list, int start = 0) => Unsafe.As<Tuple<T[]>>(list).Item1.AsSpan(start, list.Count); public static ref T Get<T>(this T[] arr, int index) { if (index < 0) return ref arr[arr.Length + index]; return ref arr[index]; } public static TValue Get<TKey, TValue>(this IDictionary<TKey, TValue> dic, TKey key) { dic.TryGetValue(key, out var v); return v; } public static TValue GetOrInit<TKey, TValue>(this IDictionary<TKey, TValue> dic, TKey key, TValue value) { if (dic.TryGetValue(key, out var v)) return v; return dic[key] = value; } } public static class ExComparer<T> { class ExpressionComparer<K> : IComparer<T> where K : IComparable<K> { private class ParameterReplaceVisitor : ExpressionVisitor { private readonly ParameterExpression from; private readonly ParameterExpression to; public ParameterReplaceVisitor(ParameterExpression from, ParameterExpression to) { this.from = from; this.to = to; } protected override Expression VisitParameter(ParameterExpression node) => node == from ? to : base.VisitParameter(node); } readonly Comparison<T> func; public ExpressionComparer(Expression<Func<T, K>> expression) { var paramA = expression.Parameters[0]; var paramB = Expression.Parameter(typeof(T)); var f2 = (Expression<Func<T, K>>)new ParameterReplaceVisitor(expression.Parameters[0], paramB).Visit(expression); var compExp = Expression.Lambda<Comparison<T>>(Expression.Call(expression.Body, typeof(K).GetMethod(nameof(IComparable<K>.CompareTo), new[] { typeof(K) }), f2.Body), paramA, paramB); this.func = compExp.Compile(); } public int Compare(T x, T y) => func(x, y); public override bool Equals(object obj) => obj is ExpressionComparer<K> c && this.func == c.func; public override int GetHashCode() => func.GetHashCode(); } class ReverseComparer : IComparer<T> { private static Comparer<T> orig = Comparer<T>.Default; public int Compare(T y, T x) => orig.Compare(x, y); public override bool Equals(object obj) => obj is ReverseComparer; public override int GetHashCode() => GetType().GetHashCode(); } public static IComparer<T> CreateExp<K>(Expression<Func<T, K>> expression) where K : IComparable<K> => new ExpressionComparer<K>(expression); public static IComparer<T> DefaultReverse => new ReverseComparer(); } public class ΔDebugView<T> { private IEnumerable<T> collection; public ΔDebugView(IEnumerable<T> collection) { this.collection = collection ?? throw new ArgumentNullException(nameof(collection)); }[DebuggerBrowsable(DebuggerBrowsableState.RootHidden)] public T[] Items => collection.ToArray(); }[DebuggerStepThrough] public class ConsoleReader { const int BufSize = 1 << 12; private readonly byte[] buffer = new byte[BufSize]; private readonly Stream input; private readonly Encoding encoding; private int pos = 0; private int len = 0; public ConsoleReader(Stream input, Encoding encoding) { this.input = input; this.encoding = encoding; } public ConsoleReader(Stream input) : this(input, Console.InputEncoding) { } private void MoveNext() { if (++pos >= len) { len = input.Read(buffer, 0, buffer.Length); if (len == 0) { buffer[0] = 10; } pos = 0; } } public int Int { [MethodImpl(MethodImplOptions.AggressiveInlining)] get { int res = 0; bool neg = false; while (buffer[pos] < 48) { neg = buffer[pos] == 45; MoveNext(); } do { res = checked(res * 10 + (buffer[pos] ^ 48)); MoveNext(); } while (48 <= buffer[pos]); return neg ? -res : res; } } public int Int0 => this.Int - 1; public long Long { [MethodImpl(MethodImplOptions.AggressiveInlining)] get { long res = 0; bool neg = false; while (buffer[pos] < 48) { neg = buffer[pos] == 45; MoveNext(); } do { res = res * 10 + (buffer[pos] ^ 48); MoveNext(); } while (48 <= buffer[pos]); return neg ? -res : res; } } public long Long0 => this.Long - 1; public string String { [MethodImpl(MethodImplOptions.AggressiveInlining)] get { var sb = new List<byte>(); while (buffer[pos] <= 32) MoveNext(); do { sb.Add(buffer[pos]); MoveNext(); } while (32 < buffer[pos]); return this.encoding.GetString(sb.ToArray()); } } public string Ascii { [MethodImpl(MethodImplOptions.AggressiveInlining)] get { var sb = new StringBuilder(); while (buffer[pos] <= 32) MoveNext(); do { sb.Append((char)buffer[pos]); MoveNext(); } while (32 < buffer[pos]); return sb.ToString(); } } public string Line { [MethodImpl(MethodImplOptions.AggressiveInlining)] get { var sb = new List<byte>(); while (buffer[pos] <= 32) MoveNext(); do { sb.Add(buffer[pos]); MoveNext(); } while (buffer[pos] != 10 && buffer[pos] != 13); return this.encoding.GetString(sb.ToArray()); } } public char Char { [MethodImpl(MethodImplOptions.AggressiveInlining)] get { while (buffer[pos] <= 32) MoveNext(); char res = (char)buffer[pos]; MoveNext(); return res; } } public double Double => double.Parse(this.Ascii);[DebuggerStepThrough] public struct RepeatReader { ConsoleReader cr; int count; public RepeatReader(ConsoleReader cr, int count) { this.cr = cr; this.count = count; } public T[] Select<T>(Func<ConsoleReader, T> factory) { var arr = new T[count]; for (var i = 0; i < count; i++) arr[i] = factory(cr); return arr; } public T[] Select<T>(Func<ConsoleReader, int, T> factory) { var arr = new T[count]; for (var i = 0; i < count; i++) arr[i] = factory(cr, i); return arr; } public string[] Line { get { var arr = new string[count]; for (var i = 0; i < count; i++) arr[i] = cr.Line; return arr; } } public string[] String { get { var arr = new string[count]; for (var i = 0; i < count; i++) arr[i] = cr.String; return arr; } } public string[] Ascii { get { var arr = new string[count]; for (var i = 0; i < count; i++) arr[i] = cr.Ascii; return arr; } } public int[] Int { get { var arr = new int[count]; for (var i = 0; i < count; i++) arr[i] = cr.Int; return arr; } } public int[] Int0 { get { var arr = new int[count]; for (var i = 0; i < count; i++) arr[i] = cr.Int0; return arr; } } public long[] Long { get { var arr = new long[count]; for (var i = 0; i < count; i++) arr[i] = cr.Long; return arr; } } public long[] Long0 { get { var arr = new long[count]; for (var i = 0; i < count; i++) arr[i] = cr.Long0; return arr; } } public double[] Double { get { var arr = new double[count]; for (var i = 0; i < count; i++) arr[i] = cr.Double; return arr; } } public static implicit operator int[](RepeatReader rr) => rr.Int; public static implicit operator long[](RepeatReader rr) => rr.Long; public static implicit operator double[](RepeatReader rr) => rr.Double; public static implicit operator string[](RepeatReader rr) => rr.Ascii; } public RepeatReader Repeat(int count) => new RepeatReader(this, count);[DebuggerStepThrough] public struct SplitReader { ConsoleReader cr; public SplitReader(ConsoleReader cr) { this.cr = cr; } public string[] String { get { while (cr.buffer[cr.pos] <= 32) cr.MoveNext(); var list = new List<string>(); do { if (cr.buffer[cr.pos] < 32) cr.MoveNext(); else list.Add(cr.String); } while (cr.buffer[cr.pos] != 10 && cr.buffer[cr.pos] != 13); return list.ToArray(); } } public string[] Ascii { get { while (cr.buffer[cr.pos] <= 32) cr.MoveNext(); var list = new List<string>(); do { if (cr.buffer[cr.pos] < 32) cr.MoveNext(); else list.Add(cr.Ascii); } while (cr.buffer[cr.pos] != 10 && cr.buffer[cr.pos] != 13); return list.ToArray(); } } public int[] Int { get { while (cr.buffer[cr.pos] <= 32) cr.MoveNext(); var list = new List<int>(); do { if (cr.buffer[cr.pos] < 32) cr.MoveNext(); else list.Add(cr.Int); } while (cr.buffer[cr.pos] != 10 && cr.buffer[cr.pos] != 13); return list.ToArray(); } } public int[] Int0 { get { while (cr.buffer[cr.pos] <= 32) cr.MoveNext(); var list = new List<int>(); do { if (cr.buffer[cr.pos] < 32) cr.MoveNext(); else list.Add(cr.Int0); } while (cr.buffer[cr.pos] != 10 && cr.buffer[cr.pos] != 13); return list.ToArray(); } } public long[] Long { get { while (cr.buffer[cr.pos] <= 32) cr.MoveNext(); var list = new List<long>(); do { if (cr.buffer[cr.pos] < 32) cr.MoveNext(); else list.Add(cr.Long); } while (cr.buffer[cr.pos] != 10 && cr.buffer[cr.pos] != 13); return list.ToArray(); } } public long[] Long0 { get { while (cr.buffer[cr.pos] <= 32) cr.MoveNext(); var list = new List<long>(); do { if (cr.buffer[cr.pos] < 32) cr.MoveNext(); else list.Add(cr.Long0); } while (cr.buffer[cr.pos] != 10 && cr.buffer[cr.pos] != 13); return list.ToArray(); } } public double[] Double { get { while (cr.buffer[cr.pos] <= 32) cr.MoveNext(); var list = new List<double>(); do { if (cr.buffer[cr.pos] < 32) cr.MoveNext(); else list.Add(cr.Double); } while (cr.buffer[cr.pos] != 10 && cr.buffer[cr.pos] != 13); return list.ToArray(); } } public static implicit operator int[](SplitReader sr) => sr.Int; public static implicit operator long[](SplitReader sr) => sr.Long; public static implicit operator double[](SplitReader sr) => sr.Double; public static implicit operator string[](SplitReader sr) => sr.Ascii; } public SplitReader Split => new SplitReader(this); public static implicit operator int(ConsoleReader cr) => cr.Int; public static implicit operator long(ConsoleReader cr) => cr.Long; public static implicit operator double(ConsoleReader cr) => cr.Double; public static implicit operator string(ConsoleReader cr) => cr.Ascii; public void Deconstruct(out ConsoleReader o1, out ConsoleReader o2) => (o1, o2) = (this, this); public void Deconstruct(out ConsoleReader o1, out ConsoleReader o2, out ConsoleReader o3) => (o1, o2, o3) = (this, this, this); public void Deconstruct(out ConsoleReader o1, out ConsoleReader o2, out ConsoleReader o3, out ConsoleReader o4) => (o1, o2, o3, o4) = (this, this, this, this); public void Deconstruct(out ConsoleReader o1, out ConsoleReader o2, out ConsoleReader o3, out ConsoleReader o4, out ConsoleReader o5) => (o1, o2, o3, o4, o5) = (this, this, this, this, this); public void Deconstruct(out ConsoleReader o1, out ConsoleReader o2, out ConsoleReader o3, out ConsoleReader o4, out ConsoleReader o5, out ConsoleReader o6) => (o1, o2, o3, o4, o5, o6) = (this, this, this, this, this, this); public void Deconstruct(out ConsoleReader o1, out ConsoleReader o2, out ConsoleReader o3, out ConsoleReader o4, out ConsoleReader o5, out ConsoleReader o6, out ConsoleReader o7) => (o1, o2, o3, o4, o5, o6, o7) = (this, this, this, this, this, this, this); public void Deconstruct(out ConsoleReader o1, out ConsoleReader o2, out ConsoleReader o3, out ConsoleReader o4, out ConsoleReader o5, out ConsoleReader o6, out ConsoleReader o7, out ConsoleReader o8) => (o1, o2, o3, o4, o5, o6, o7, o8) = (this, this, this, this, this, this, this, this); }[DebuggerStepThrough] public class ConsoleWriter {[DebuggerBrowsable(DebuggerBrowsableState.Never)] public readonly StreamWriter sw; public ConsoleWriter(Stream output) : this(output, Console.OutputEncoding) { } public ConsoleWriter(Stream output, Encoding encoding) { sw = new StreamWriter(output, encoding); } public void Flush() => sw.Flush(); public ConsoleWriter WriteLine(ReadOnlySpan<char> obj) { sw.WriteLine(obj); return this; } public ConsoleWriter WriteLine<T>(T obj) { sw.WriteLine(obj.ToString()); return this; } public ConsoleWriter WriteLineJoin<T>(ReadOnlySpan<T> col) => WriteMany(' ', col); public ConsoleWriter WriteLineJoin<T>(IEnumerable<T> col) => WriteMany(' ', col); public ConsoleWriter WriteLines<T>(ReadOnlySpan<T> col) => WriteMany('\n', col); public ConsoleWriter WriteLines<T>(IEnumerable<T> col) => WriteMany('\n', col); public ConsoleWriter WriteLineGrid<T>(IEnumerable<IEnumerable<T>> cols) { var en = cols.GetEnumerator(); while (en.MoveNext()) WriteLineJoin(en.Current); return this; } private ConsoleWriter WriteMany<T>(char sep, ReadOnlySpan<T> col) { var en = col.GetEnumerator(); if (!en.MoveNext()) return this; sw.Write(en.Current.ToString()); while (en.MoveNext()) { sw.Write(sep); sw.Write(en.Current.ToString()); } sw.WriteLine(); return this; } private ConsoleWriter WriteMany<T>(char sep, IEnumerable<T> col) { var en = col.GetEnumerator(); if (!en.MoveNext()) return this; sw.Write(en.Current.ToString()); while (en.MoveNext()) { sw.Write(sep); sw.Write(en.Current.ToString()); } sw.WriteLine(); return this; } } }
public partial class Program {[System.Diagnostics.DebuggerBrowsable(System.Diagnostics.DebuggerBrowsableState.Never)] public ConsoleReader cr;[System.Diagnostics.DebuggerBrowsable(System.Diagnostics.DebuggerBrowsableState.Never)] public ConsoleWriter cw; public Program(ConsoleReader reader, ConsoleWriter writer) { this.cr = reader; this.cw = writer; System.Globalization.CultureInfo.CurrentCulture = System.Globalization.CultureInfo.InvariantCulture; } static void Main() => new Program(new ConsoleReader(Console.OpenStandardInput()), new ConsoleWriter(Console.OpenStandardOutput())).Run(); public void Run() { var res = Calc(); if (res is double) cw.WriteLine(Result((double)res)); else if (res is bool) cw.WriteLine(Result((bool)res)); else if (res != null) cw.WriteLine(res.ToString()); cw.Flush(); } }
public partial class Program
{
    public static string Result(double d) => d.ToString("0.####################", System.Globalization.CultureInfo.InvariantCulture);
    #endregion
    public static string Result(bool b) => b ? "Yes" : "No";
    private object Calc()
    {
        H = cr;
        W = cr;
        (int h, int w) start = (cr.Int0, cr.Int0);
        (int h, int w) goal = (cr.Int0, cr.Int0);
        grid = cr.Repeat(H).Ascii;
        bfs = NewArray(H, W, (int)1e9);
        var pq = new PriorityQueue<int, (int h, int w)>(H * W);
        pq.Add(0, start);
        bfs[start.h][start.w] = 0;

        while (pq.Count > 0)
        {
            var (v, (h, w)) = pq.Dequeue();
            if (v > bfs[h][w]) continue;

            for (int ht = -2; ht <= 2; ht++)
                for (int wt = -2; wt <= 2; wt++)
                {
                    var nh = h + ht;
                    var nw = w + wt;
                    switch (Math.Abs(ht) + Math.Abs(wt))
                    {
                        case 0:
                            break;
                        case 1:
                            if (Update(nh, nw, v))
                                pq.Add(v, (nh, nw));
                            break;
                        default:
                            if (Update(nh, nw, v + 1))
                                pq.Add(v + 1, (nh, nw));
                            break;
                    }
                }

        }

        var res = bfs[goal.h][goal.w];
        if (res > (int)1e8) return -1;
        return res;
    }
    bool Update(int h, int w, int v)
    {
        if (h < 0 || w < 0 || H <= h || W <= w) return false;
        if (grid[h][w] == '#') return false;
        return bfs[h][w].UpdateMin(v);
    }

    int[][] bfs;
    int H;
    int W;
    string[] grid;
}


[System.Diagnostics.DebuggerDisplay("Count = {" + nameof(Count) + "}")] class PriorityQueue<T> { protected readonly List<T> data; protected readonly IComparer<T> comparer; public PriorityQueue() : this(Comparer<T>.Default) { } public PriorityQueue(int capacity) : this(capacity, Comparer<T>.Default) { } public PriorityQueue(IComparer<T> comparer) { this.data = new List<T>(); this.comparer = comparer; } public PriorityQueue(int capacity, IComparer<T> comparer) { this.data = new List<T>(capacity); this.comparer = comparer; }[System.Diagnostics.DebuggerBrowsable(System.Diagnostics.DebuggerBrowsableState.Never)] public int Count => data.Count; public T Peek => data[0]; public void Add(T value) { data.Add(value); UpdateUp(data.Count - 1); } public T Dequeue() { var res = data[0]; data[0] = data[^1]; data.RemoveAt(data.Count - 1); UpdateDown(0); return res; } private void UpdateUp(int i) { if (i > 0) { var p = (i - 1) >> 1; if (comparer.Compare(data[i], data[p]) < 0) { (data[p], data[i]) = (data[i], data[p]); UpdateUp(p); } } } private void UpdateDown(int i) { var n = data.Count; var child = 2 * i + 1; if (child < n) { if (child != n - 1 && comparer.Compare(data[child], data[child + 1]) > 0) child++; if (comparer.Compare(data[i], data[child]) > 0) { (data[child], data[i]) = (data[i], data[child]); UpdateDown(child); } } }[System.Diagnostics.DebuggerBrowsable(System.Diagnostics.DebuggerBrowsableState.RootHidden)] private T[] Items => data.ToArray().Sort((a, b) => comparer.Compare(a, b)); }
class PriorityQueue<TKey, TValue> : PriorityQueue<KeyValuePair<TKey, TValue>> { private class KeyComparer : IComparer<KeyValuePair<TKey, TValue>> { public readonly IComparer<TKey> comparer; public KeyComparer(IComparer<TKey> comparer) { this.comparer = comparer; } public int Compare(KeyValuePair<TKey, TValue> x, KeyValuePair<TKey, TValue> y) => comparer.Compare(x.Key, y.Key); } public PriorityQueue() : this(Comparer<TKey>.Default) { } public PriorityQueue(int capacity) : this(capacity, Comparer<TKey>.Default) { } public PriorityQueue(IComparer<TKey> comparer) : base(new KeyComparer(comparer)) { } public PriorityQueue(int capacity, IComparer<TKey> comparer) : base(capacity, new KeyComparer(comparer)) { } public void Add(TKey key, TValue value) => Add(new KeyValuePair<TKey, TValue>(key, value)); }