提出 #31867979

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ソースコード 拡げる

using System;
using System.Collections;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Numerics;

namespace Tasks
{
    public class D
    {
        public static void Main()
        {
            var sw = new StreamWriter(Console.OpenStandardOutput()) { AutoFlush = false };
            Console.SetOut(sw);
            Solve();
            Console.Out.Flush();
        }

        public static void Solve()
        {
            var N = Scanner.Scan<int>();
            var A = Scanner.ScanEnumerable<int>().ToArray();
            var count = new int[(int)2e5 + 1];
            foreach (var a in A)
            {
                count[a]++;
            }

            var B = count.Where(x => x > 0).ToArray();
            var M = B.Length;

            var cumK = new long[M + 1];
            var cumJ = new long[M + 1];
            for (var k = M - 1; k >= 0; k--)
            {
                cumK[k] = B[k] + cumK[k + 1];
            }

            for (var j = M - 2; j >= 0; j--)
            {
                cumJ[j] = B[j] * cumK[j + 1] + cumJ[j + 1];
            }

            long answer = 0;
            for (var i = 0; i + 2 < M; i++)
            {
                answer += B[i] * cumJ[i + 1];
            }

            Console.WriteLine(answer);
        }

        public static class Scanner
        {
            public static string ScanLine() => Console.ReadLine()?.Trim() ?? string.Empty;
            public static string[] Scan() => ScanLine().Split(' ');
            public static T Scan<T>() where T : IConvertible => Convert<T>(Scan()[0]);
            public static (T1, T2) Scan<T1, T2>() where T1 : IConvertible where T2 : IConvertible
            {
                var line = Scan();
                return (Convert<T1>(line[0]), Convert<T2>(line[1]));
            }
            public static (T1, T2, T3) Scan<T1, T2, T3>() where T1 : IConvertible where T2 : IConvertible where T3 : IConvertible
            {
                var line = Scan();
                return (Convert<T1>(line[0]), Convert<T2>(line[1]), Convert<T3>(line[2]));
            }
            public static (T1, T2, T3, T4) Scan<T1, T2, T3, T4>() where T1 : IConvertible where T2 : IConvertible where T3 : IConvertible where T4 : IConvertible
            {
                var line = Scan();
                return (Convert<T1>(line[0]), Convert<T2>(line[1]), Convert<T3>(line[2]), Convert<T4>(line[3]));
            }
            public static (T1, T2, T3, T4, T5) Scan<T1, T2, T3, T4, T5>() where T1 : IConvertible where T2 : IConvertible where T3 : IConvertible where T4 : IConvertible where T5 : IConvertible
            {
                var line = Scan();
                return (Convert<T1>(line[0]), Convert<T2>(line[1]), Convert<T3>(line[2]), Convert<T4>(line[3]), Convert<T5>(line[4]));
            }
            public static (T1, T2, T3, T4, T5, T6) Scan<T1, T2, T3, T4, T5, T6>() where T1 : IConvertible where T2 : IConvertible where T3 : IConvertible where T4 : IConvertible where T5 : IConvertible where T6 : IConvertible
            {
                var line = Scan();
                return (Convert<T1>(line[0]), Convert<T2>(line[1]), Convert<T3>(line[2]), Convert<T4>(line[3]), Convert<T5>(line[4]), Convert<T6>(line[5]));
            }
            public static IEnumerable<T> ScanEnumerable<T>() where T : IConvertible => Scan().Select(Convert<T>);
            private static T Convert<T>(string value) where T : IConvertible => (T)System.Convert.ChangeType(value, typeof(T));
        }
    }
}

提出情報

ジャッジ結果