提出 #70420180

---

ソースコード 拡げる

using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
using System.Text;

#pragma warning disable CS8603, CS8604, CS8602


namespace ProblemC
{
    internal class TEST
    {
        public static void Main()
        {
            Sol mySol = new Sol();
            mySol.Solve();
        }
    }

    internal class Sol
    {
        public void Solve()
        {
            var di = new Dictionary<long, long>();
            foreach(var n in A){
                if (!di.ContainsKey(n)) di.Add(n, 0);
                di[n]++;
            }

            long tot = 0;
            foreach(var k in di.Keys){
                if (di[k] < 2) continue;
                long c = di[k] * (di[k] - 1) / 2 * (N - di[k]);
                tot += c;
            }

            Console.WriteLine(tot);

        }
        int N;
        long[] A;
        public Sol()
        {
            N = ri();
            A = rla();
        }

        static String rs() { return Console.ReadLine(); }
        static int ri() { return int.Parse(Console.ReadLine()); }
        static long rl() { return long.Parse(Console.ReadLine()); }
        static double rd() { return double.Parse(Console.ReadLine()); }
        static String[] rsa(char sep = ' ') { return Console.ReadLine().Split(sep); }
        static int[] ria(char sep = ' ') { return Array.ConvertAll(Console.ReadLine().Split(sep), e => int.Parse(e)); }
        static long[] rla(char sep = ' ') { return Array.ConvertAll(Console.ReadLine().Split(sep), e => long.Parse(e)); }
        static double[] rda(char sep = ' ') { return Array.ConvertAll(Console.ReadLine().Split(sep), e => double.Parse(e)); }
        static T[] mka<T>(int n, T ini) { T[] ret = new T[n]; for (int i = 0; i < n; i++) ret[i] = ini; return ret; }
        static T[][] mka<T>(int n, int m, T ini) { T[][] ret = new T[n][]; for (int i = 0; i < n; i++) ret[i] = mka(m, ini); return ret; }
        static T[][][] mka<T>(int n, int m, int l, T ini) { T[][][] ret = new T[n][][]; for (int i = 0; i < n; i++) ret[i] = mka(m, l, ini); return ret; }
        static T[][][][] mka<T>(int n, int m, int l, int k, T ini) { T[][][][] ret = new T[n][][][]; for (int i = 0; i < n; i++) ret[i] = mka(m, l, k, ini); return ret; }
        static T[] mka<T>(int n) where T : new() { T[] ret = new T[n]; for (int i = 0; i < n; i++) ret[i] = new T(); return ret; }
        static T[][] mka<T>(int n, int m) where T : new() { T[][] ret = new T[n][]; for (int i = 0; i < n; i++) ret[i] = mka<T>(m); return ret; }
        static T[][][] mka<T>(int n, int m, int l) where T : new() { T[][][] ret = new T[n][][]; for (int i = 0; i < n; i++) ret[i] = mka<T>(m, l); return ret; }
        static T[][][][] mka<T>(int n, int m, int l, int k) where T : new() { T[][][][] ret = new T[n][][][]; for (int i = 0; i < n; i++) ret[i] = mka<T>(m, l, k); return ret; }

    }

}

提出情報

ジャッジ結果