#55517 (C#(csc)) No.275 中央値を求めよ

• 問題: No.275 中央値を求めよ
• ユーザー: 紙ぺーぱー
• 提出日時: 2015-10-24 03:46:43
• 言語: C#(csc) (csc 3.9.0)
• 結果: WA (最新)
  AC
  (最初)
• 実行時間: -
• コード長: 7,479 bytes
• コンパイル時間: 2,387 ms
• コンパイル使用メモリ: 110,464 KB
• 実行使用メモリ: 18,688 KB
• 最終ジャッジ日時: 2024-06-07 15:44:57
• 合計ジャッジ時間: 4,371 ms
• ジャッジサーバーID （参考情報）: judge2 / judge1

入力	結果	実行時間; 実行使用メモリ
testcase_00	AC	22 ms; 18,688 KB
testcase_01	AC	23 ms; 18,304 KB
testcase_02	AC	23 ms; 18,432 KB
testcase_03	AC	22 ms; 18,432 KB
testcase_04	AC	22 ms; 18,688 KB
testcase_05	AC	23 ms; 18,560 KB
testcase_06	AC	22 ms; 18,560 KB
testcase_07	AC	23 ms; 18,688 KB
testcase_08	AC	23 ms; 18,432 KB
testcase_09	AC	22 ms; 18,432 KB
testcase_10	WA	-
testcase_11	AC	21 ms; 18,176 KB
testcase_12	AC	23 ms; 18,432 KB
testcase_13	AC	22 ms; 18,688 KB
testcase_14	AC	23 ms; 18,688 KB
testcase_15	AC	23 ms; 18,688 KB
testcase_16	AC	23 ms; 18,560 KB
testcase_17	AC	23 ms; 18,176 KB
testcase_18	AC	21 ms; 18,688 KB
testcase_19	AC	21 ms; 18,560 KB
testcase_20	AC	23 ms; 18,176 KB
testcase_21	AC	23 ms; 18,304 KB
testcase_22	AC	24 ms; 18,688 KB
testcase_23	AC	22 ms; 18,560 KB
testcase_24	AC	22 ms; 18,688 KB
testcase_25	AC	23 ms; 18,432 KB
testcase_26	AC	21 ms; 18,432 KB
testcase_27	AC	23 ms; 18,432 KB
testcase_28	AC	23 ms; 18,432 KB
testcase_29	AC	23 ms; 18,560 KB
testcase_30	AC	22 ms; 18,560 KB
testcase_31	AC	22 ms; 18,432 KB
testcase_32	AC	20 ms; 18,560 KB
testcase_33	AC	21 ms; 18,432 KB
testcase_34	AC	21 ms; 18,432 KB
testcase_35	AC	22 ms; 18,304 KB
testcase_36	AC	21 ms; 18,688 KB
testcase_37	AC	22 ms; 18,432 KB
testcase_38	AC	22 ms; 18,176 KB
testcase_39	AC	22 ms; 18,688 KB
testcase_40	AC	22 ms; 18,432 KB

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

using System;
using System.Linq;
using System.Diagnostics;
using System.Collections.Generic;
using Debug = System.Diagnostics.Debug;
using StringBuilder = System.Text.StringBuilder;
using System.Numerics;
using Number = System.Int32;
namespace Program
{

    public class Solver
    {
        public void Solve()
        {
            var n = sc.Integer();
            var a = sc.Integer(n);
            if (n % 2 == 1)
                IO.Printer.Out.WriteLine(Algorithm.QuickSelect(a, n / 2));
            else
            {
                var l = Algorithm.QuickSelect(a, (n / 2) - 1);
                var r = Algorithm.QuickSelect(a, n / 2);
                IO.Printer.Out.Write((l + r) / 2);
                if (((l + r) & 1) == 1)
                    IO.Printer.Out.WriteLine(".5");
                else IO.Printer.Out.WriteLine();

            }

        }
        public IO.StreamScanner sc = new IO.StreamScanner(Console.OpenStandardInput());
        static T[] Enumerate<T>(int n, Func<int, T> f) { var a = new T[n]; for (int i = 0; i < n; ++i) a[i] = f(i); return a; }
        static public void Swap<T>(ref T a, ref T b) { var tmp = a; a = b; b = tmp; }
    }
}

#region main
static class Ex
{
    static public string AsString(this IEnumerable<char> ie) { return new string(System.Linq.Enumerable.ToArray(ie)); }
    static public string AsJoinedString<T>(this IEnumerable<T> ie, string st = " ") { return string.Join(st, ie); }
    static public void Main()
    {
        var solver = new Program.Solver();
        solver.Solve();
        Program.IO.Printer.Out.Flush();
    }
}
#endregion
#region Ex
namespace Program.IO
{
    using System.IO;
    using System.Text;
    using System.Globalization;
    public class Printer : StreamWriter
    {
        static Printer() { Out = new Printer(Console.OpenStandardOutput()) { AutoFlush = false }; }
        public static Printer Out { get; set; }
        public override IFormatProvider FormatProvider { get { return CultureInfo.InvariantCulture; } }
        public Printer(System.IO.Stream stream) : base(stream, new UTF8Encoding(false, true)) { }
        public Printer(System.IO.Stream stream, Encoding encoding) : base(stream, encoding) { }
        public void Write<T>(string format, T[] source) { base.Write(format, source.OfType<object>().ToArray()); }
        public void WriteLine<T>(string format, T[] source) { base.WriteLine(format, source.OfType<object>().ToArray()); }
    }
    public class StreamScanner
    {
        public StreamScanner(Stream stream) { str = stream; }
        public readonly Stream str;
        private readonly byte[] buf = new byte[1024];
        private int len, ptr;
        public bool isEof = false;
        public bool IsEndOfStream { get { return isEof; } }
        private byte read()
        {
            if (isEof) return 0;
            if (ptr >= len) { ptr = 0; if ((len = str.Read(buf, 0, 1024)) <= 0) { isEof = true; return 0; } }
            return buf[ptr++];
        }
        public char Char() { byte b = 0; do b = read(); while ((b < 33 || 126 < b) && !isEof); return (char)b; }

        public string Scan()
        {
            var sb = new StringBuilder();
            for (var b = Char(); b >= 33 && b <= 126; b = (char)read())
                sb.Append(b);
            return sb.ToString();
        }
        public string ScanLine()
        {
            var sb = new StringBuilder();
            for (var b = Char(); b != '\n'; b = (char)read())
                if (b == 0) break;
                else if (b != '\r') sb.Append(b);
            return sb.ToString();
        }
        public long Long()
        {
            if (isEof) return long.MinValue;
            long ret = 0; byte b = 0; var ng = false;
            do b = read();
            while (b != '-' && (b < '0' || '9' < b));
            if (b == '-') { ng = true; b = read(); }
            for (; true; b = read())
            {
                if (b < '0' || '9' < b)
                    return ng ? -ret : ret;
                else ret = ret * 10 + b - '0';
            }
        }
        public int Integer() { return (isEof) ? int.MinValue : (int)Long(); }
        public double Double() { return double.Parse(Scan(), CultureInfo.InvariantCulture); }
        private T[] enumerate<T>(int n, Func<T> f)
        {
            var a = new T[n];
            for (int i = 0; i < n; ++i) a[i] = f();
            return a;
        }

        public char[] Char(int n) { return enumerate(n, Char); }
        public string[] Scan(int n) { return enumerate(n, Scan); }
        public double[] Double(int n) { return enumerate(n, Double); }
        public int[] Integer(int n) { return enumerate(n, Integer); }
        public long[] Long(int n) { return enumerate(n, Long); }
    }
}
#endregion
#region QuickSelect
static public partial class Algorithm
{
    /// <summary>
    /// k番目に小さな値を取得する.O(N)
    /// </summary>
    static public Number QuickSelect(Number[] a, int k)
    {
        return QuickSelect(a, k, 0, a.Length);
    }
    /// <summary>
    /// k番目に小さな値を取得する.O(N)
    /// </summary>
    static public Number QuickSelect(Number[] a, int k, int l, int r)
    {
        var pivot = RandomPivot(a, l, r);
        //var pivot = MediansOfMedian(a,l,r);
        //for (int p = r - 1; p >= l; p--) if (a[p] == pivot) { a[p] = a[r - 1]; ; a[r - 1] = pivot; break; }
        int i = l; var j = r - 2;
        while (true)
        {
            while (i < r - 1 && a[i] < pivot) i++;
            while (j >= l && a[j] >= pivot) j--;
            if (i >= j) break;
            var tmp = a[i];
            a[i] = a[j];
            a[j] = tmp;
            //a[i] ^= a[j]; a[j] ^= a[i]; a[i] ^= a[j];
        }
        a[r - 1] = a[i]; a[i] = pivot;
        if (k < i - l) return QuickSelect(a, k, l, i);
        else if (k == i - l) return pivot;
        else return QuickSelect(a, k - (i - l + 1), i + 1, r);
    }
    static Random rand = new Random();
    /// <summary>
    /// ランダムにピボットを取る
    /// </summary>
    static public Number RandomPivot(this Number[] a, int l, int r)
    {
        var pos = rand.Next(l, r);
        var tmp = a[pos]; a[pos] = a[r - 1]; a[r - 1] = tmp;
        return a[r - 1];
    }
    /// <summary>
    /// だいたいの中央値を取る,O(N)だが遅い
    /// </summary>
    static public Number MediansOfMedian(this Number[] a, int l, int r)
    {
        var med = new Number[5];
        var n = r - l;
        if (n <= 5)
        {
            for (int i = 0; i <= n / 2; i++)
            {
                var min = i;
                for (int j = i + 1; j < n; j++)
                    if (a[l + min] > a[l + j]) min = j;
                var tmp = a[l + min];
                a[l + min] = a[l + i];
                a[l + i] = tmp;
            }
            return a[l + (n / 2)];
        }
        var res = new Number[n / 5];
        for (int i = 0; i < n / 5; i++)
        {
            for (int j = 0; j < 5; j++)
                med[j] = a[l + i * 5 + j];
            for (int j = 0; j < 3; j++)
            {
                var min = j;
                for (int k = j + 1; k < 5; k++)
                    if (med[min] > med[k]) { min = k; }
                var tmp = med[min];
                med[min] = med[j];
                med[j] = tmp;
            }
            res[i] = med[2];
        }
        return MediansOfMedian(res, 0, res.Length);

    }

}
#endregion