結果
問題 | No.1300 Sum of Inversions |
ユーザー |
![]() |
提出日時 | 2020-11-27 22:21:04 |
言語 | C#(csc) (csc 3.9.0) |
結果 |
AC
|
実行時間 | 824 ms / 2,000 ms |
コード長 | 28,522 bytes |
コンパイル時間 | 2,374 ms |
コンパイル使用メモリ | 130,408 KB |
実行使用メモリ | 59,948 KB |
最終ジャッジ日時 | 2024-07-26 13:23:08 |
合計ジャッジ時間 | 25,071 ms |
ジャッジサーバーID (参考情報) |
judge5 / judge1 |
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ファイルパターン | 結果 |
---|---|
sample | AC * 3 |
other | AC * 34 |
コンパイルメッセージ
Microsoft (R) Visual C# Compiler version 3.9.0-6.21124.20 (db94f4cc) Copyright (C) Microsoft Corporation. All rights reserved.
ソースコード
// ReSharper disable RedundantUsingDirectiveusing System;using System.Collections.Generic;using System.Collections.ObjectModel;using System.Diagnostics;using System.Runtime.CompilerServices;using System.IO;using System.Linq;using System.Numerics;using static Solve.Methods;using static Solve.Input;using static Solve.Output;using static System.Math;// Resharper restore RedundantUsingDirectiveusing Solve.Libraries.ModInt;using Solve.Libraries.SegmentTree.SegmentTree;namespace Solve{public partial class Solver {public void Main() {int N = Int;var A = Long.array(N);var memo = A.Select((x, i) => (x, i)).ToArray().Sort();var conv = new int[N];for (int i = 0; i < N; i++) {conv[memo[i].i] = i;}var seg = new SegmentTree<(ModInt sum, long cnt)>(N,(a, b) => (a.sum + b.sum, a.cnt + b.cnt),(0, 0));seg.Build();var B = new (ModInt, long)[N];for (int i = 0; i < N; i++) {var idx = conv[i];seg.Update(idx, (A[i], 1));var (val, cnt) = seg.Query(idx + 1, N);B[i] = (val + A[i] * cnt, cnt);}var seg2 = new SegmentTree<(ModInt sum, long cnt)>(N,(a, b) => (a.sum + b.sum, a.cnt + b.cnt),(0, 0));var C = new ModInt[N];for (int i = 0; i < N; i++) {var idx = conv[i];seg2.Update(idx, B[i]);var (val, cnt) = seg2.Query(idx + 1, N);C[i] = val + (ModInt)A[i] * cnt;}var ans = ModInt.Zero;foreach (var l in C) {ans += l;}print(ans);}public const int MOD = 1000000007;}public static class Methods{[MethodImpl(256)] public static bool Assert(in bool b, in string message = null) =>b ? true : throw new Exception(message ?? "Assert failed.");[MethodImpl(256)] public static string JoinSpace<T>(this IEnumerable<T> source) => source.Join(" ");[MethodImpl(256)] public static string JoinEndline<T>(this IEnumerable<T> source) => source.Join("\n");[MethodImpl(256)] public static string Join<T>(this IEnumerable<T> source, string s) => string.Join(s, source);[MethodImpl(256)] public static string Join<T>(this IEnumerable<T> source, char c) =>string.Join(c.ToString(), source);public static int Gcd(int a, int b) => (int) Gcd((long) a, b);public static long Gcd(long a, long b) {while (true) {if (a < b) (a, b) = (b, a);if (a % b == 0) return b;(a, b) = (b, a % b);}}public static long Lcm(long a, long b) => a / Gcd(a, b) * b;public static bool IsPrime(long value) {if (value <= 1) return false;for (long i = 2; i * i <= value; ++i) if (value % i == 0) return false;return true;}public static long Pow(long a, int b) {long res = 1;while (b > 0) { if (b % 2 != 0) res *= a; a *= a; b >>= 1; }return res;}public static int PowMod(long a, long b, int p) => (int) PowMod(a, b, (long) p);public static long PowMod(long a, long b, long p) {long res = 1;while (b > 0) { if (b % 2 != 0) res = res * a % p; a = a * a % p; b >>= 1; }return res;}public static IEnumerable<long> Factors(long n) {Assert(n >= 0, "n must be greater than 0.");for (long i = 1; i * i <= n; ++i) {var div = DivRem(n, i, out var rem);if (rem > 0) continue;yield return div;if (i != div) yield return i;}}public static IEnumerable<int> Factors(int n) => Factors((long) n).Select(Convert.ToInt32);[MethodImpl(256)] public static int DivCeil(int a, int b) => (a + b - 1) / b;[MethodImpl(256)] public static long DivCeil(long a, long b) => (a + b - 1) / b;public static IEnumerable<T[]> Permutations<T>(IEnumerable<T> src) {var ret = new List<T[]>();Search(ret, new Stack<T>(), src.ToArray());return ret;static void Search(ICollection<T[]> perms, Stack<T> stack, T[] a) {int N = a.Length;if (N == 0) perms.Add(stack.Reverse().ToArray());else {var b = new T[N - 1];Array.Copy(a, 1, b, 0, N - 1);for (int i = 0; i < a.Length; ++i) {stack.Push(a[i]);Search(perms, stack, b);if (i < b.Length) b[i] = a[i];stack.Pop();}}}}public static long BinarySearch(long low, long high, Func<long, bool> expression) {while (low < high) {long middle = (high - low) / 2 + low;if (!expression(middle))high = middle;elselow = middle + 1;}return high;}public static int LowerBound<T>(T[] arr, int start, int end, T value, IComparer<T> comparer) {int low = start;int high = end;while (low < high) {var mid = ((high - low) >> 1) + low;if (comparer.Compare(arr[mid], value) < 0)low = mid + 1;elsehigh = mid;}return low;}public static int LowerBound<T>(T[] arr, T value) where T : IComparable =>LowerBound(arr, 0, arr.Length, value, Comparer<T>.Default);public static int UpperBound<T>(T[] arr, int start, int end, T value, IComparer<T> comparer) {var (low, high) = (start, end);while (low < high) {var mid = ((high - low) >> 1) + low;if (comparer.Compare(arr[mid], value) <= 0) low = mid + 1;else high = mid;}return low;}public static int UpperBound<T>(T[] arr, T value) =>UpperBound(arr, 0, arr.Length, value, Comparer<T>.Default);[MethodImpl(256)]public static IEnumerable<TResult> Repeat<TResult>(TResult value, int count) => Enumerable.Repeat(value, count);[MethodImpl(256)] public static string AsString(this IEnumerable<char> source) => new string(source.ToArray());public static IEnumerable<long> CumSum(this IEnumerable<long> source) {long sum = 0; foreach (var item in source) yield return sum += item;}public static IEnumerable<int> CumSum(this IEnumerable<int> source) {int sum = 0; foreach (var item in source) yield return sum += item;}[MethodImpl(256)] public static bool IsIn<T>(this T value, T l, T r) where T : IComparable<T> =>l.CompareTo(r) > 0 ? throw new ArgumentException() : l.CompareTo(value) <= 0 && value.CompareTo(r) < 0;[MethodImpl(256)] public static bool IsIn(this in int value, in Range range) =>value.IsIn(range.Start.Value, range.End.Value);[MethodImpl(256)] public static bool IsIn(this in Index value, in Range range) =>value.IsFromEnd && value.Value.IsIn(range.Start.Value, range.End.Value);public static IEnumerable<int> Range(int start, int end, int step = 1) {for (var i = start; i < end; i += step) yield return i;}public static IEnumerable<int> Range(int end) => Range(0, end);public static IEnumerable<int> Range(Range range, int step = 1) =>Range(range.Start.Value, range.End.Value, step);[MethodImpl(256)] public static T[] Sort<T>(this T[] arr) where T : IComparable<T> {var array = arr[..]; Array.Sort(array); return array;}[MethodImpl(256)]public static T[] Sort<T, U>(this T[] arr, Func<T, U> selector) where U : IComparable<U> {var array = arr[..];Array.Sort(array, (a, b) => selector(a).CompareTo(selector(b)));return array;}[MethodImpl(256)] public static T[] SortDescending<T>(this T[] arr) where T : IComparable<T> {var array = arr[..];Array.Sort(array, (a, b) => b.CompareTo(a));return array;}[MethodImpl(256)]public static T[] SortDescending<T, U>(this T[] arr, Func<T, U> selector) where U : IComparable<U> {var array = arr[..];Array.Sort(array, (a, b) => selector(b).CompareTo(selector(a)));return array;}public static T[] Unique<T>(this IEnumerable<T> arr) {var source = arr.ToArray();var ret = new List<T>(source.Length);var set = new SortedSet<T>();ret.AddRange(source.Where(val => set.Add(val)));return ret.ToArray();}[MethodImpl(256)] public static bool chmin<T>(ref T a, T b)where T : IComparable<T> {if (a.CompareTo(b) > 0) { a = b; return true; }return false;}[MethodImpl(256)] public static bool chmax<T>(ref T a, T b)where T : IComparable<T> {if (a.CompareTo(b) < 0) { a = b; return true; }return false;}public static T[] InitArray<T>(int n, Func<int, T> init) {var res = new T[n];for (int i = 0; i < n; i++) res[i] = init(i);return res;}public static T[][] JaggedArray2D<T>(int a, int b, T defaultValue = default) {var ret = new T[a][];for (int i = 0; i < a; ++i) ret[i] = Enumerable.Repeat(defaultValue, b).ToArray();return ret;}public static T[,] Array2D<T>(int a, int b, T defaultValue = default) {var ret = new T[a, b];for (int i = 0; i < a; ++i) for (int j = 0; j < b; ++j) ret[i, j] = defaultValue;return ret;}public static T[,] To2DArray<T>(this T[][] array) {if (!array.Any()) return new T[0, 0];int len = array[0].Length;if (array.Any(x => x.Length != len))throw new ArgumentException("Length of each array must be same.", nameof(array));var ret = new T[array.Length, len];for (int i = 0; i < array.Length; ++i) for (int j = 0; j < len; ++j) ret[i, j] = array[i][j];return ret;}[MethodImpl(256)] public static T Min<T>(params T[] col) => col.Min();[MethodImpl(256)] public static T Max<T>(params T[] col) => col.Max();[MethodImpl(256)] public static IEnumerable<(T, int)> WithIndex<T>(this IEnumerable<T> source) =>source.Select((x, i) => (x, i));[MethodImpl(256)] public static (T, U, V)[] Zip<T, U, V>(IReadOnlyCollection<T> t,IReadOnlyCollection<U> u,IReadOnlyCollection<V> v) {Assert(t.Count == u.Count && u.Count == v.Count);return t.Zip(u, (a, b) => (a, b)).Zip(v, (tuple, c) => (tuple.Item1, tuple.Item2, c)).ToArray();}[MethodImpl(256)] public static void rep(in int start, in int end, Action<int> func) {for (int i = start; i < end; ++i) func(i);}[MethodImpl(256)] public static void rep(in int end, Action<int> func) => rep(0, end, func);[MethodImpl(256)] public static void rep1(in int end, Action<int> func) => rep(1, end + 1, func);[MethodImpl(256)] public static void repr(in int end, Action<int> func) {for (int i = end - 1; i >= 0; --i) func(i);}[MethodImpl(256)]public static void each<T>(this IEnumerable<T> source, Action<T> func) {foreach (var item in source) func(item);}[MethodImpl(256)]public static void eachWithIndex<T>(this IEnumerable<T> source, Action<T, int> func) {int index = 0; foreach (var item in source) func(item, index++);}[MethodImpl(256)] public static int bit(in int x) => 1 << x;[MethodImpl(256)] public static long bitl(in int x) => 1L << x;}public class UnorderedMap<T, U> : Dictionary<T, U>{public new U this[T k] {get =>TryGetValue(k, out var v) ? v : base[k] = default;set =>base[k] = value;}}public class Map<T, U> : SortedDictionary<T, U>{readonly U _default;public Map(U defaultValue = default) {_default = defaultValue;}public new U this[T k] {get =>TryGetValue(k, out var v) ? v : base[k] = _default;set =>base[k] = value;}}public class Scanner<T>{public T r => next<T>();public T next() => r;IEnumerable<T> enumerable(int N) { for (int i = 0; i < N; ++i) yield return r; }public T[] array(in int N) => enumerable(N).ToArray();public List<T> list(in int N) => enumerable(N).ToList();public T[,] array2d(in int N, in int M) => next2DArray<T>(N, M);public T[][] listArray(in int n) {var ret = new T[n][];for (int i = 0; i < n; i++) ret[i] = array(next<int>());return ret;}public void Deconstruct(out T _1, out T _2) => (_1, _2) = (r, r);public void Deconstruct(out T _1, out T _2, out T _3) => (_1, _2, _3) = (r, r, r);public void Deconstruct(out T _1, out T _2, out T _3, out T _4) =>(_1, _2, _3, _4) = (r, r, r, r);public void Deconstruct(out T _1, out T _2, out T _3, out T _4, out T _5) =>(_1, _2, _3, _4, _5) = (r, r, r, r, r);public void Deconstruct(out T _1, out T _2, out T _3, out T _4, out T _5, out T _6) =>(_1, _2, _3, _4, _5, _6) = (r, r, r, r, r, r);public void Deconstruct(out T _1, out T _2, out T _3, out T _4, out T _5, out T _6, out T _7) =>(_1, _2, _3, _4, _5, _6, _7) = (r, r, r, r, r, r, r);public void Deconstruct(out T _1, out T _2, out T _3, out T _4, out T _5, out T _6, out T _7, out T _8) =>(_1, _2, _3, _4, _5, _6, _7, _8) = (r, r, r, r, r, r, r, r);public void Deconstruct(out T _1, out T _2, out T _3, out T _4,out T _5, out T _6, out T _7, out T _8, out T _9) =>(_1, _2, _3, _4, _5, _6, _7, _8, _9) = (r, r, r, r, r, r, r, r, r);public void Deconstruct(out T _1, out T _2, out T _3, out T _4,out T _5, out T _6, out T _7, out T _8, out T _9, out T _10) =>(_1, _2, _3, _4, _5, _6, _7, _8, _9, _10) = (r, r, r, r, r, r, r, r, r, r);public static implicit operator T(Scanner<T> sc) => sc.r;}public static class Input{const char _separator = ' ';static readonly Queue<string> _input = new Queue<string>();static readonly StreamReader sr =#if FILEnew StreamReader("in.txt");#elsenew StreamReader(Console.OpenStandardInput());#endifpublic static string ReadLine => sr.ReadLine();static string ReadStr => Read;static int ReadInt => int.Parse(Read);static long ReadLong => long.Parse(Read);static ulong ReadULong => ulong.Parse(Read);static double ReadDouble => double.Parse(Read);static BigInteger ReadBigInteger => BigInteger.Parse(Read);public static string Read {get {if (_input.Any()) return _input.Dequeue();foreach (var val in sr.ReadLine().Split(_separator)) _input.Enqueue(val);return _input.Dequeue();}}public static string next() => Read;public static T next<T>() =>default(T) switch {sbyte _ => (T) (object) (sbyte) ReadInt,short _ => (T) (object) (short) ReadInt,int _ => (T) (object) ReadInt,long _ => (T) (object) ReadLong,byte _ => (T) (object) (byte) ReadULong,ushort _ => (T) (object) (ushort) ReadULong,uint _ => (T) (object) (uint) ReadULong,ulong _ => (T) (object) ReadULong,float _ => (T) (object) (float) ReadDouble,double _ => (T) (object) ReadDouble,string _ => (T) (object) ReadStr,char _ => (T) (object) ReadStr[0],BigInteger _ => (T) (object) ReadBigInteger,_ => typeof(T) == typeof(string)? (T) (object) ReadStr: throw new NotSupportedException(),};public static (T, U) next<T, U>() => (next<T>(), next<U>());public static (T, U, V) next<T, U, V>() => (next<T>(), next<U>(), next<V>());public static (T, U, V, W) next<T, U, V, W>() => (next<T>(), next<U>(), next<V>(), next<W>());public static (T, U, V, W, X) next<T, U, V, W, X>() => (next<T>(), next<U>(), next<V>(), next<W>(), next<X>());public static T[] nextArray<T>(in int size) {var ret = new T[size]; for (int i = 0; i < size; ++i) ret[i] = next<T>(); return ret;}public static T[,] next2DArray<T>(int n, in int m) {var ret = new T[n, m];for (int i = 0; i < n; ++i) for (int j = 0; j < n; ++j) ret[i, j] = next<T>(); return ret;}public static (T[], U[]) nextArray<T, U>(in int size) {var ret1 = new T[size]; var ret2 = new U[size];for (int i = 0; i < size; ++i) (ret1[i], ret2[i]) = next<T, U>();return (ret1, ret2);}public static (T[], U[], V[]) nextArray<T, U, V>(in int size) {var ret1 = new T[size]; var ret2 = new U[size]; var ret3 = new V[size];for (int i = 0; i < size; ++i) (ret1[i], ret2[i], ret3[i]) = next<T, U, V>();return (ret1, ret2, ret3);}}public static class Output{[MethodImpl(256)] public static void print() => Console.WriteLine();[MethodImpl(256)] public static void print(in string s, bool endline = true) {if (endline) Console.WriteLine(s); else Console.Write(s);}[MethodImpl(256)] public static void print(in char s, bool endline = true) {if (endline) Console.WriteLine(s); else Console.Write(s);}[MethodImpl(256)] public static void print(in int v, bool endline = true) {if (endline) Console.WriteLine(v); else Console.Write(v);}[MethodImpl(256)] public static void print(in long v, bool endline = true) {if (endline) Console.WriteLine(v); else Console.Write(v);}[MethodImpl(256)] public static void print(in ulong v, bool endline = true) {if (endline) Console.WriteLine(v); else Console.Write(v);}[MethodImpl(256)] public static void print(in bool b) => PrintBool(b);[MethodImpl(256)] public static void print(in object v) => Console.WriteLine(v);[MethodImpl(256)] public static void print<T>(in IEnumerable<T> array, string separator = " ") =>Console.WriteLine(array.Join(separator));[MethodImpl(256)] public static void prints<T>(params T[] t) => print(t);#if LOCAL[MethodImpl(256)] public static void debug<T>(in T value, bool endline = true) {if (endline) Console.WriteLine(value);else Console.Write(value);}#elsepublic static void debug(params object[] obj) { }#endif[MethodImpl(256)] static void PrintBool(in bool val, in string yes = null, in string no = null) =>print(val ? yes ?? _yes : no ?? _no);static string _yes = "Yes", _no = "No";public static void SetYesNoString(in YesNoType t) => (_yes, _no) = YesNoString[t];public static void SetYesNoString(in string yes, in string no) => (_yes, _no) = (yes, no);static readonly Dictionary<YesNoType, (string yes, string no)>YesNoString = new Dictionary<YesNoType, (string, string)> {{YesNoType.Yes_No, ("Yes", "No")},{YesNoType.YES_NO, ("YES", "NO")},{YesNoType.Upper, ("YES", "NO")},{YesNoType.yes_no, ("yes", "no")},{YesNoType.Lower, ("yes", "no")},{YesNoType.Possible_Impossible, ("Possible", "Impossible")},{YesNoType.Yay, ("Yay!", ":(")},};public static readonly (string yes, string no) YN_Possible = ("Possible", "Impossible"),YN_lower = ("yes", "no"), YN_upper = ("YES", "NO"), YN_Yay = ("Yay!", ":(");public static void Yes() => print(_yes);public static void No() => print(_no);public static object cout { set => Console.WriteLine(value); }#if LOCALpublic static object dout { set => Console.WriteLine(value); }#elsepublic static object dout { set { } }#endifpublic static object cerr { set => Console.Error.WriteLine(value); }public const string endl = "\n";public enum YesNoType { Yes_No, YES_NO, Upper, yes_no, Lower, Possible_Impossible, Yay }}public class Program{public static void Main(string[] args) {var sw = new StreamWriter(Console.OpenStandardOutput()) {AutoFlush = false};Console.SetOut(sw);new Solver().Main();Console.Out.Flush();}}partial class Solver{readonly Scanner<int> Int;readonly Scanner<long> Long;readonly Scanner<string> String;public Solver() => (Int, String, Long) = (new Scanner<int>(), new Scanner<string>(), new Scanner<long>());const int INF = 1000000010;const long LINF = 1000000000000000100;const double EPS = 1e-9;public static readonly int[] dx = {-1, 0, 0, 1, -1, -1, 1, 1}, dy = {0, 1, -1, 0, -1, 1, -1, 1};}}namespace Solve.Libraries.ModInt{[DebuggerDisplay("{" + nameof(_value) + "}")]public struct ModInt : IEquatable<ModInt>, IComparable<ModInt> {public const int MOD = 998_244_353; //1_000_000_007;long _value;public static readonly ModInt Zero = new ModInt(0);public static readonly ModInt One = new ModInt(1);public ModInt(in long value) => _value = (value % MOD + MOD) % MOD;public int Value => (int) _value;public ModInt Invert => ModPow(this, MOD - 2);public static ModInt operator -(ModInt value) {value._value = MOD - value._value;return value;}public static ModInt operator +(ModInt left, in ModInt right) {left._value += right._value;if (left._value >= MOD) left._value -= MOD;return left;}public static ModInt operator -(ModInt left, in ModInt right) {left._value -= right._value;if (left._value < 0) left._value += MOD;return left;}public static ModInt operator *(ModInt left, in ModInt right) => left._value * right._value % MOD;public static ModInt operator /(ModInt left, in ModInt right) => left * right.Invert;public static ModInt operator ++(ModInt value) {if (value._value == MOD - 1) value._value = 0;else value._value++;return value;}public static ModInt operator --(ModInt value) {if (value._value == 0) value._value = MOD - 1;else value._value--;return value;}public static bool operator ==(ModInt left, in ModInt right) => left.Equals(right);public static bool operator !=(ModInt left, in ModInt right) => !left.Equals(right);public static implicit operator ModInt(in int value) => new ModInt(value);public static implicit operator ModInt(in long value) => new ModInt(value);public static explicit operator int(ModInt m) => m.Value;public static ModInt ModPow(ModInt value, long exponent) {var r = new ModInt(1);for (; exponent > 0; value *= value, exponent >>= 1)if ((exponent & 1) == 1)r *= value;return r;}public static ModInt ModFact(int value) {var r = new ModInt(1);for (var i = 2; i <= value; i++) r *= value;return r;}public bool Equals(ModInt other) => _value == other._value;public override bool Equals(object obj) => obj is ModInt m && Equals(m);public override int GetHashCode() => _value.GetHashCode();public override string ToString() => _value.ToString();public int CompareTo(ModInt other) => _value.CompareTo(other._value);}}namespace Solve.Libraries.SegmentTree.SegmentTree{public class SegmentTree<T>{readonly int _size;readonly T[] _seg;readonly Func<T, T, T> _func;readonly T _identity;public SegmentTree(int N, Func<T, T, T> func, T identity = default) {_func = func;_identity = identity;_size = 1 << (int) System.Math.Ceiling(System.Math.Log(N, 2));_seg = Enumerable.Repeat(_identity, _size * 2).ToArray();}public void Set(int i, T value) {if (i < 0 || i >= _size) throw new ArgumentOutOfRangeException(nameof(i));_seg[_size + i] = value;}public void Build() {for (int i = _size - 1; i > 0; i--) _seg[i] = _func(_seg[2 * i], _seg[2 * i + 1]);}public void Update(int i, T value) {i += _size;_seg[i] = value;while ((i >>= 1) > 0) _seg[i] = _func(_seg[2 * i], _seg[2 * i + 1]);}public T Query(int l, int r) {T L = _identity, R = _identity;for (l += _size, r += _size; l < r; l >>= 1, r >>= 1) {if ((l & 1) > 0) L = _func(L, _seg[l++]);if ((r & 1) > 0) R = _func(_seg[--r], R);}return _func(L, R);}public int FindSubtree(int a, Func<T, bool> check, T M, bool type) {int t = type ? 1 : 0;while (a < _size) {var nxt = type ? _func(_seg[2 * a + t], M) : _func(M, _seg[2 * a + t]);if (check(nxt)) a = 2 * a + t;else (M, a) = (nxt, 2 * a + 1 - t);}return a - _size;}public int FindFirst(int a, Func<T, bool> check) {var L = _identity;if (a <= 0) {if (check(_func(L, _seg[1]))) return FindSubtree(1, check, L, false);return -1;}int b = _size;for (a += _size, b += _size; a < b; a >>= 1, b >>= 1) {if ((a & 1) != 0) {var nxt = _func(L, _seg[a]);if (check(nxt)) return FindSubtree(a, check, L, false);L = nxt;++a;}}return -1;}public int FindLast(int b, Func<T, bool> check) {var R = _identity;if (b >= _size) {if (check(_func(_seg[1], R))) return FindSubtree(1, check, R, true);return -1;}int a = _size;for (b += _size; a < b; a >>= 1, b >>= 1) {if ((b & 1) != 0) {var nxt = _func(_seg[--b], R);if (check(nxt)) return FindSubtree(b, check, R, true);R = nxt;}}return -1;}public T this[int i] => _seg[i + _size];}}