using System; using System.Buffers; using System.Collections.Generic; using System.Diagnostics; using System.IO; using System.Linq; using System.Numerics; using System.Runtime.CompilerServices; using System.Runtime.InteropServices; using System.Runtime.Intrinsics.X86; using System.Text; using YukicoderContest308.Problems; namespace YukicoderContest308.Problems { public class ProblemD : ProblemBase { public ProblemD() : base(false) { } [MethodImpl(MethodImplOptions.AggressiveOptimization)] protected override void SolveEach(IOManager io) { var n = io.ReadInt(); var totalRow = n * (n - 1) / 2; var maxR = "0"; var uf = new UnionFind(n); for (int i = 0; i < totalRow; i++) { var a = io.ReadInt(); var b = io.ReadInt(); var c = io.ReadString(); a--; b--; if (uf.Unite(a, b)) { maxR = c; } } io.WriteLine(maxR); } public class PriorityQueue : IEnumerable where T : IComparable { const int InitialSize = 4; private readonly int _reverseFactor; private T[] _heap; public int Count { get; private set; } public bool IsDescending => _reverseFactor == 1; public PriorityQueue(Order order) { _reverseFactor = order == Order.Ascending ? -1 : 1; _heap = new T[InitialSize]; Count = 0; } public PriorityQueue(Order order, IEnumerable collection) : this(order) { foreach (var item in collection) { Enqueue(item); } } public void Enqueue(T item) { if (Count >= _heap.Length) { var temp = new T[_heap.Length << 1]; _heap.AsSpan().CopyTo(temp); _heap = temp; } var index = Count++; ref var child = ref _heap[index]; child = item; while (index > 0) { index = (index - 1) >> 1; ref var parent = ref _heap[index]; if (Compare(child, parent) <= 0) { break; } Swap(ref child, ref parent); child = ref parent; } } public T Dequeue() { var index = 0; ref var parent = ref _heap[index]; var item = parent; parent = _heap[--Count]; var span = _heap.AsSpan(0, Count); while (true) { index = (index << 1) + 1; if (unchecked((uint)index < (uint)span.Length)) { ref var child = ref span[index]; var r = index + 1; if (unchecked((uint)r < (uint)span.Length)) { ref var brother = ref span[r]; if (Compare(child, brother) < 0) { child = ref brother; index = r; } } if (Compare(parent, child) < 0) { Swap(ref parent, ref child); parent = ref child; } else { break; } } else { break; } } return item; } public T Peek() => _heap[0]; public void Clear() => Count = 0; private int Compare(T a, T b) => _reverseFactor * a.CompareTo(b); private void Swap(ref T a, ref T b) { var temp = a; a = b; b = temp; } public IEnumerator GetEnumerator() { var copy = new T[_heap.Length]; var cnt = Count; _heap.AsSpan().CopyTo(copy); try { while (Count > 0) { yield return Dequeue(); } } finally { _heap = copy; Count = cnt; } } System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator() => GetEnumerator(); public enum Order { Ascending, Descending } } public class UnionFind { private int[] _parentsOrSizes; public int Count => _parentsOrSizes.Length; public int Groups { get; private set; } public UnionFind(int count) { _parentsOrSizes = new int[count]; _parentsOrSizes.AsSpan().Fill(-1); Groups = _parentsOrSizes.Length; } [MethodImpl(MethodImplOptions.AggressiveInlining)] public bool Unite(int a, int b) { var x = GetLeader(a); var y = GetLeader(b); if (x == y) { return false; } else { if (-_parentsOrSizes[x] < _parentsOrSizes[y]) { (x, y) = (y, x); } _parentsOrSizes[x] += _parentsOrSizes[y]; _parentsOrSizes[y] = x; Groups--; return true; } } public bool IsInSameGroup(int a, int b) => GetLeader(a) == GetLeader(b); [MethodImpl(MethodImplOptions.AggressiveInlining)] public int GetLeader(int index) { if (index >= _parentsOrSizes.Length) { ThrowArgumentException(); } return GetLeaderRecursive(index); int GetLeaderRecursive(int index) { if (unchecked((uint)_parentsOrSizes[index]) < _parentsOrSizes.Length) { return _parentsOrSizes[index] = GetLeaderRecursive(_parentsOrSizes[index]); } else { return index; } } } public int GetGroupSize(int index) => -_parentsOrSizes[GetLeader(index)]; public int[][] GetAllGroups() { var resultIndices = ArrayPool.Shared.Rent(_parentsOrSizes.Length); var index = 0; var results = new int[Groups][]; for (int i = 0; i < _parentsOrSizes.Length; i++) { if (_parentsOrSizes[i] < 0) { results[index] = new int[-_parentsOrSizes[i]]; resultIndices[i] = index++; } } var counts = new int[results.Length]; for (int i = 0; i < _parentsOrSizes.Length; i++) { var group = resultIndices[GetLeader(i)]; results[group][counts[group]++] = i; } ArrayPool.Shared.Return(resultIndices); return results; } private void ThrowArgumentException() => throw new ArgumentException(); } } } namespace YukicoderContest308 { class Program { static void Main(string[] args) { IProblem question = new ProblemD(); using var io = new IOManager(Console.OpenStandardInput(), Console.OpenStandardOutput()); question.Solve(io); } } } #region Base Class namespace YukicoderContest308.Problems { public interface IProblem { string Solve(string input); void Solve(IOManager io); } public abstract class ProblemBase : IProblem { protected bool HasMultiTestCases { get; } protected ProblemBase(bool hasMultiTestCases) => HasMultiTestCases = hasMultiTestCases; public string Solve(string input) { var inputStream = new MemoryStream(Encoding.UTF8.GetBytes(input)); var outputStream = new MemoryStream(); using var manager = new IOManager(inputStream, outputStream); Solve(manager); manager.Flush(); outputStream.Seek(0, SeekOrigin.Begin); var reader = new StreamReader(outputStream); return reader.ReadToEnd(); } public void Solve(IOManager io) { var tests = HasMultiTestCases ? io.ReadInt() : 1; for (var t = 0; t < tests; t++) { SolveEach(io); } } protected abstract void SolveEach(IOManager io); } } #endregion #region Utils namespace YukicoderContest308 { public class IOManager : IDisposable { private readonly BinaryReader _reader; private readonly StreamWriter _writer; private bool _disposedValue; private byte[] _buffer = new byte[1024]; private int _length; private int _cursor; private bool _eof; const char ValidFirstChar = '!'; const char ValidLastChar = '~'; public IOManager(Stream input, Stream output) { _reader = new BinaryReader(input); _writer = new StreamWriter(output) { AutoFlush = false }; } [MethodImpl(MethodImplOptions.AggressiveInlining)] private char ReadAscii() { if (_cursor == _length) { _cursor = 0; _length = _reader.Read(_buffer); if (_length == 0) { if (!_eof) { _eof = true; return char.MinValue; } else { ThrowEndOfStreamException(); } } } return (char)_buffer[_cursor++]; } [MethodImpl(MethodImplOptions.AggressiveInlining)] public char ReadChar() { char c; while (!IsValidChar(c = ReadAscii())) { } return c; } [MethodImpl(MethodImplOptions.AggressiveInlining)] public string ReadString() { var builder = new StringBuilder(); char c; while (!IsValidChar(c = ReadAscii())) { } do { builder.Append(c); } while (IsValidChar(c = ReadAscii())); return builder.ToString(); } public int ReadInt() => (int)ReadLong(); [MethodImpl(MethodImplOptions.AggressiveInlining)] public long ReadLong() { long result = 0; bool isPositive = true; char c; while (!IsNumericChar(c = ReadAscii())) { } if (c == '-') { isPositive = false; c = ReadAscii(); } do { result *= 10; result += c - '0'; } while (IsNumericChar(c = ReadAscii())); return isPositive ? result : -result; } [MethodImpl(MethodImplOptions.AggressiveInlining)] private Span ReadChunk(Span span) { var i = 0; char c; while (!IsValidChar(c = ReadAscii())) { } do { span[i++] = c; } while (IsValidChar(c = ReadAscii())); return span.Slice(0, i); } [MethodImpl(MethodImplOptions.AggressiveInlining)] public double ReadDouble() => double.Parse(ReadChunk(stackalloc char[32])); [MethodImpl(MethodImplOptions.AggressiveInlining)] public decimal ReadDecimal() => decimal.Parse(ReadChunk(stackalloc char[32])); public int[] ReadIntArray(int n) { var a = new int[n]; for (int i = 0; i < a.Length; i++) { a[i] = ReadInt(); } return a; } public long[] ReadLongArray(int n) { var a = new long[n]; for (int i = 0; i < a.Length; i++) { a[i] = ReadLong(); } return a; } public double[] ReadDoubleArray(int n) { var a = new double[n]; for (int i = 0; i < a.Length; i++) { a[i] = ReadDouble(); } return a; } public decimal[] ReadDecimalArray(int n) { var a = new decimal[n]; for (int i = 0; i < a.Length; i++) { a[i] = ReadDecimal(); } return a; } [MethodImpl(MethodImplOptions.AggressiveInlining)] public void Write(T value) => _writer.Write(value.ToString()); [MethodImpl(MethodImplOptions.AggressiveInlining)] public void WriteLine(T value) => _writer.WriteLine(value.ToString()); public void WriteLine(IEnumerable values, char separator) { var e = values.GetEnumerator(); if (e.MoveNext()) { _writer.Write(e.Current.ToString()); while (e.MoveNext()) { _writer.Write(separator); _writer.Write(e.Current.ToString()); } } _writer.WriteLine(); } public void WriteLine(T[] values, char separator) => WriteLine((ReadOnlySpan)values, separator); public void WriteLine(Span values, char separator) => WriteLine((ReadOnlySpan)values, separator); public void WriteLine(ReadOnlySpan values, char separator) { for (int i = 0; i < values.Length - 1; i++) { _writer.Write(values[i]); _writer.Write(separator); } if (values.Length > 0) { _writer.Write(values[^1]); } _writer.WriteLine(); } public void Flush() => _writer.Flush(); [MethodImpl(MethodImplOptions.AggressiveInlining)] private static bool IsValidChar(char c) => ValidFirstChar <= c && c <= ValidLastChar; [MethodImpl(MethodImplOptions.AggressiveInlining)] private static bool IsNumericChar(char c) => ('0' <= c && c <= '9') || c == '-'; private void ThrowEndOfStreamException() => throw new EndOfStreamException(); protected virtual void Dispose(bool disposing) { if (!_disposedValue) { if (disposing) { _reader.Dispose(); _writer.Flush(); _writer.Dispose(); } _disposedValue = true; } } public void Dispose() { Dispose(disposing: true); GC.SuppressFinalize(this); } } public static class UtilExtensions { public static bool ChangeMax(ref this T value, T other) where T : struct, IComparable { if (value.CompareTo(other) < 0) { value = other; return true; } return false; } public static bool ChangeMin(ref this T value, T other) where T : struct, IComparable { if (value.CompareTo(other) > 0) { value = other; return true; } return false; } public static void SwapIfLargerThan(ref this T a, ref T b) where T : struct, IComparable { if (a.CompareTo(b) > 0) { (a, b) = (b, a); } } public static void SwapIfSmallerThan(ref this T a, ref T b) where T : struct, IComparable { if (a.CompareTo(b) < 0) { (a, b) = (b, a); } } public static void Sort(this T[] array) where T : IComparable => Array.Sort(array); public static void Sort(this T[] array, Comparison comparison) => Array.Sort(array, comparison); } public static class CollectionExtensions { private class ArrayWrapper { #pragma warning disable CS0649 public T[] Array; #pragma warning restore CS0649 } [MethodImpl(MethodImplOptions.AggressiveInlining)] public static Span AsSpan(this List list) { return Unsafe.As>(list).Array.AsSpan(0, list.Count); } [MethodImpl(MethodImplOptions.AggressiveInlining)] public static Span GetRowSpan(this T[,] array, int i) { var width = array.GetLength(1); return MemoryMarshal.CreateSpan(ref array[i, 0], width); } [MethodImpl(MethodImplOptions.AggressiveInlining)] public static Span GetRowSpan(this T[,,] array, int i, int j) { var width = array.GetLength(2); return MemoryMarshal.CreateSpan(ref array[i, j, 0], width); } [MethodImpl(MethodImplOptions.AggressiveInlining)] public static Span GetRowSpan(this T[,,,] array, int i, int j, int k) { var width = array.GetLength(3); return MemoryMarshal.CreateSpan(ref array[i, j, k, 0], width); } public static void Fill(this T[] array, T value) => array.AsSpan().Fill(value); public static void Fill(this T[,] array, T value) => MemoryMarshal.CreateSpan(ref array[0, 0], array.Length).Fill(value); public static void Fill(this T[,,] array, T value) => MemoryMarshal.CreateSpan(ref array[0, 0, 0], array.Length).Fill(value); public static void Fill(this T[,,,] array, T value) => MemoryMarshal.CreateSpan(ref array[0, 0, 0, 0], array.Length).Fill(value); } public static class SearchExtensions { struct LowerBoundComparer : IComparer where T : IComparable { public int Compare(T x, T y) => 0 <= x.CompareTo(y) ? 1 : -1; } struct UpperBoundComparer : IComparer where T : IComparable { public int Compare(T x, T y) => 0 < x.CompareTo(y) ? 1 : -1; } // https://trsing.hatenablog.com/entry/2019/08/27/211038 public static int GetGreaterEqualIndex(this ReadOnlySpan span, T inclusiveMin) where T : IComparable => ~span.BinarySearch(inclusiveMin, new UpperBoundComparer()); public static int GetGreaterThanIndex(this ReadOnlySpan span, T exclusiveMin) where T : IComparable => ~span.BinarySearch(exclusiveMin, new LowerBoundComparer()); public static int GetLessEqualIndex(this ReadOnlySpan span, T inclusiveMax) where T : IComparable => ~span.BinarySearch(inclusiveMax, new LowerBoundComparer()) - 1; public static int GetLessThanIndex(this ReadOnlySpan span, T exclusiveMax) where T : IComparable => ~span.BinarySearch(exclusiveMax, new UpperBoundComparer()) - 1; public static int GetGreaterEqualIndex(this Span span, T inclusiveMin) where T : IComparable => ((ReadOnlySpan)span).GetGreaterEqualIndex(inclusiveMin); public static int GetGreaterThanIndex(this Span span, T exclusiveMin) where T : IComparable => ((ReadOnlySpan)span).GetGreaterThanIndex(exclusiveMin); public static int GetLessEqualIndex(this Span span, T inclusiveMax) where T : IComparable => ((ReadOnlySpan)span).GetLessEqualIndex(inclusiveMax); public static int GetLessThanIndex(this Span span, T exclusiveMax) where T : IComparable => ((ReadOnlySpan)span).GetLessThanIndex(exclusiveMax); public static int BoundaryBinarySearch(Predicate predicate, int ok, int ng) { while (Math.Abs(ok - ng) > 1) { var mid = (ok + ng) / 2; if (predicate(mid)) { ok = mid; } else { ng = mid; } } return ok; } public static long BoundaryBinarySearch(Predicate predicate, long ok, long ng) { while (Math.Abs(ok - ng) > 1) { var mid = (ok + ng) / 2; if (predicate(mid)) { ok = mid; } else { ng = mid; } } return ok; } public static BigInteger BoundaryBinarySearch(Predicate predicate, BigInteger ok, BigInteger ng) { while (BigInteger.Abs(ok - ng) > 1) { var mid = (ok + ng) / 2; if (predicate(mid)) { ok = mid; } else { ng = mid; } } return ok; } public static double BoundaryBinarySearch(Predicate predicate, double ok, double ng, double eps = 1e-9, int loopLimit = 1000) { var count = 0; while (Math.Abs(ok - ng) > eps && count++ < loopLimit) { var mid = (ok + ng) * 0.5; if (predicate(mid)) { ok = mid; } else { ng = mid; } } return (ok + ng) * 0.5; } public static double Bisection(Func f, double a, double b, double eps = 1e-9, int loopLimit = 100) { double mid = (a + b) / 2; var fa = f(a); if (fa * f(b) >= 0) { throw new ArgumentException("f(a)とf(b)は異符号である必要があります。"); } for (int i = 0; i < loopLimit; i++) { var fmid = f(mid); var sign = fa * fmid; if (sign < 0) { b = mid; } else if (sign > 0) { a = mid; fa = fmid; } else { return mid; } mid = (a + b) / 2; if (Math.Abs(b - a) < eps) { break; } } return mid; } } } #endregion