Problem:
Score : 300 points

Problem Statement

We will call a string obtained by arranging the characters contained in a string a in some order, an anagram of a.

For example, greenbin is an anagram of beginner. As seen here, when the same character occurs multiple times, that character must be used that number of times.

Given are N strings s_1, s_2, \ldots, s_N. Each of these strings has a length of 10 and consists of lowercase English characters. Additionally, all of these strings are distinct. Find the number of pairs of integers i, j (1 \leq i < j \leq N) such that s_i is an anagram of s_j.

Constraints

2 \leq N \leq 10^5

s_i is a string of length 10.

Each character in s_i is a lowercase English letter.

s_1, s_2, \ldots, s_N are all distinct.

Input

Input is given from Standard Input in the following format:

N
s_1
s_2
:
s_N

Output

Print the number of pairs of integers i, j (1 \leq i < j \leq N) such that s_i is an anagram of s_j.

Sample Input 1

3
acornistnt
peanutbomb
constraint

Sample Output 1

1

s_1 = acornistnt is an anagram of s_3 = constraint. There are no other pairs i, j such that s_i is an anagram of s_j, so the answer is 1.

Sample Input 2

2
oneplustwo
ninemodsix

Sample Output 2

0

If there is no pair i, j such that s_i is an anagram of s_j, print 0.

Sample Input 3

5
abaaaaaaaa
oneplustwo
aaaaaaaaba
twoplusone
aaaabaaaaa

Sample Output 3

4

Note that the answer may not fit into a 32-bit integer type, though we cannot put such a case here.

Solution in C# (Mono 4.6.2.0) (judge verdict: Accepted)

namespace AtCoder
{
    using System;
    using System.Collections.Generic;
    using System.IO;
    using System.Linq;
    using System.Text;
    using static System.Console;
    using static System.Math;
    using static Util;

    class AtCoder
    {
        /*------------------------------------------------------------------*/

        void Solve()
        {
            int N;
            string[] s;
            io.i(out N);
            io.ini(out s, N);

            var cnts = new Counts<string>();
            var ans = 0L;
            foreach (var _s in s.Select(x => x.Sort()))
            {
                if (cnts.ContainsKey(_s))
                {
                    ans += cnts[_s];
                }
                cnts.Add(_s);
            }

            WriteLine(ans);
            
        }

        /*------------------------------------------------------------------*/
        void Test()
        {
            //--- TEST ---//
        }

        public static void Main(string[] _) => new AtCoder().Stream();
        IO io = new IO();

        private void Stream()
        {
            /*
            var exStdIn = new System.IO.StreamReader("stdin.txt");
            SetIn(exStdIn);
            Test();
            */
            Solve();
            io.Flush();
        }
    }

    class IO
    {
        #region INPUT

        #region FastRead

        private const int Size = 1 << 12;
        private readonly Stream _stream = OpenStandardInput();
        private readonly byte[] _buffer = new byte[Size];
        private int _ptr = 0, _buffLen = 0;

        private bool HasNextByte()
        {
            if (_ptr < _buffLen) return true;
            _ptr = 0;
            _buffLen = _stream.Read(_buffer, 0, Size);
            return _buffLen > 0;
        }

        private byte ReadByte()
        {
            if (HasNextByte()) return _buffer[_ptr++];
            else
                //inputの末尾の改行がないとerror
                throw new EndOfStreamException();
        }

        private bool IsAscii(int c) => '!' <= c && c <= '~';

        private char NextChar()
        {
            var b = ReadByte();
            while (!IsAscii(b)) b = ReadByte();
            return (char) b;
        }

        private string Next()
        {
            var sb = new StringBuilder();
            for (var b = NextChar(); IsAscii(b); b = (char) ReadByte()) sb.Append(b);
            return sb.ToString();
        }

        public string String => Next();
        public char Char => NextChar();
        public int Int => int.Parse(Next());
        public long Long => long.Parse(Next());
        public double Double => double.Parse(Next());

        #endregion

        #region LazyRead

        private void scan<T>(ref T x)
        {
            if (x is int) __refvalue(__makeref(x), int) = int.Parse(Next());
            else if (x is long) __refvalue(__makeref(x), long) = long.Parse(Next());
            else if (x is double) __refvalue(__makeref(x), double) = double.Parse(Next());
            else if (x is char) __refvalue(__makeref(x), char) = NextChar();
            else __refvalue(__makeref(x), string) = Next();
        }

        public void i<T>(out T t)
        {
            t = default(T);
            scan(ref t);
        }

        public void i<T, TU>(out T t, out TU u)
        {
            i(out t);
            i(out u);
        }

        public void i<T, TU, TV>(out T t, out TU u, out TV v)
        {
            i(out t, out u);
            i(out v);
        }

        public void i<T, TU, TV, TW>(out T t, out TU u, out TV v, out TW w)
        {
            i(out t, out u);
            i(out v, out w);
        }

        public void i<T, TU, TV, TW, TX>(out T t, out TU u, out TV v, out TW w, out TX x)
        {
            i(out t, out u, out v);
            i(out w, out x);
        }

        public void i<T, TU, TV, TW, TX, TY>(out T t, out TU u, out TV v, out TW w, out TX x, out TY y)
        {
            i(out t, out u, out v);
            i(out w, out x, out y);
        }

        public void ini<T>(out T[] a, int n)
        {
            a = new T[n];
            for (int i = 0; i < n; ++i) i<T>(out a[i]);
        }

        public void ini<T, TU>(out T[] a, out TU[] b, int n)
        {
            a = new T[n];
            b = new TU[n];
            for (int i = 0; i < n; ++i) i<T, TU>(out a[i], out b[i]);
        }

        public void ini<T, TU, TV>(out T[] a, out TU[] b, out TV[] c, int n)
        {
            a = new T[n];
            b = new TU[n];
            c = new TV[n];
            for (var i = 0; i < n; ++i) i<T, TU, TV>(out a[i], out b[i], out c[i]);
        }

        public void ini<T>(out T[,] a, int h, int w)
        {
            a = new T[h, w];
            for (int i = 0; i < h; ++i)
            for (int j = 0; j < w; ++j)
                i<T>(out a[i, j]);
        }

        #endregion

        #endregion

        #region OUTPUT

        private readonly StreamWriter _sw = new StreamWriter(OpenStandardOutput())
        {
#if DEBUG
            AutoFlush = true
#else
        AutoFlush = false
#endif
        };

        public void Flush() => Out.Flush();
        public void YN(bool f) => yn(f, "YES", "NO");
        public void Yn(bool f) => yn(f, "Yes", "No");
        public void yn(bool f, string y = "yes", string n = "no") => WriteLine(f ? y : n);

        #endregion

        public IO()
        {
            SetOut(_sw);
        }
    }

    static class Util
    {
        public static void FOR(int a, int b, Action<int> f) => FOR(a, b, 1, f);

        public static void FOR(int a, int b, int n, Action<int> f)
        {
            for (int i = a; i < b; i += n) f(i);
        }

        public static void FOREQ(int a, int b, int n, Action<int> f) => FOR(a, b + 1, n, f);
        public static void FOREQ(int a, int b, Action<int> f) => FOR(a, b + 1, f);
        public static void REP(int a, Action<int> f) => FOR(0, a, f);
        public static void REPEQ(int a, Action<int> f) => FOR(0, a + 1, f);

        public static IEnumerable<TResult> ZIP<T1, T2, TResult>(IEnumerable<T1> xs, IEnumerable<T2> ys,
            Func<T1, T2, TResult> f = null)
        {
            using (var e1 = xs.GetEnumerator())
            using (var e2 = ys.GetEnumerator())
                while (e1.MoveNext() && e2.MoveNext())
                    yield return f(e1.Current, e2.Current);
        }

        public static IEnumerable<Tuple<T1, T2>> ZIP<T1, T2>(IEnumerable<T1> xs, IEnumerable<T2> ys)
            => ZIP(xs, ys, (x, y) => new Tuple<T1, T2>(x, y));

        public static IEnumerable<TResult> ZIP<T1, T2, T3, TResult>(IEnumerable<T1> xs, IEnumerable<T2> ys,
            IEnumerable<T3> zs, Func<T1, T2, T3, TResult> f)
        {
            using (var e1 = xs.GetEnumerator())
            using (var e2 = ys.GetEnumerator())
            using (var e3 = zs.GetEnumerator())
                while (e1.MoveNext() && e2.MoveNext() && e3.MoveNext())
                    yield return f(e1.Current, e2.Current, e3.Current);
        }

        public static IEnumerable<Tuple<T1, T2, T3>> ZIP<T1, T2, T3>(IEnumerable<T1> xs, IEnumerable<T2> ys,
            IEnumerable<T3> zs) => ZIP(xs, ys, zs, (x, y, z) => new Tuple<T1, T2, T3>(x, y, z));

        public static bool ODD(int x) => x % 2 != 0;
        public static bool ODD(long x) => x % 2L != 0L;

        public static T MAX<T>(params T[] xs) => xs.Max();

        public static T MIN<T>(params T[] xs) => xs.Min();

        public static int SUM(params int[] xs) => xs.Sum();
        public static long SUM(params long[] xs) => xs.Sum();

        public static IEnumerable<int> RANGE(int start, int step = 1)
        {
            var v = start;
            while (true)
            {
                yield return v;
                v += step;
            }
        }

        public struct IndexedItem<T>
        {
            public int Idx;
            public T Val;

            public IndexedItem(int idx, T val)
            {
                Idx = idx;
                Val = val;
            }
        }

        public class Counts<T> : Dictionary<T, int>
        {
            public Counts()
            {
            }

            public Counts(params T[] xs) : this()
            {
                Add(xs);
            }

            public Counts(IEnumerable<T> xs) : this()
            {
                foreach (var x in xs) Add(x);
            }

            public new int this[T key]
            {
                get
                {
                    int v;
                    return this.TryGetValue(key, out v) ? v : 0;
                }
            }

            public void Add(T key)
            {
                if (!base.ContainsKey(key)) base.Add(key, 0);
                base[key]++;
            }

            public void Add(params T[] xs) => xs.Iter(Add);

            public void SortByCount(bool isAsc) =>
                (isAsc ? (this.OrderBy(kp => kp.Value)) : (this.OrderByDescending(kp => kp.Value)))
                .ThenBy(kp => kp.Key);
        }

        public class PriorityQueue<T> where T : IComparable<T>
        {
            private List<T> heap;
            private readonly bool isAsc;
            private int size;
            public T Peek => heap[0];
            public int Count => size;
            public bool Any => size > 0;
            public bool Empty => !Any;

            public IEnumerable<T> Values => heap;

            public PriorityQueue(bool isAsc = true)
            {
                this.isAsc = isAsc;
                size = 0;
                heap = new List<T>();
            }

            public void Enqueue(T item)
            {
                heap.Add(item);
                var i = size++;
                while (i > 0)
                {
                    var p = (i - 1) / 2;
                    if (Compare(heap[p], item) <= 0) break;
                    heap[i] = heap[p];
                    i = p;
                }

                heap[i] = item;
            }

            public T Dequeue()
            {
                var ret = heap[0];
                var x = heap[--size];
                var i = 0;
                while ((i << 1) + 1 < size)
                {
                    var a = (i << 1) + 1;
                    var b = (i << 1) + 2;
                    if (b < size && Compare(heap[b], heap[a]) < 0) a = b;
                    if (Compare(heap[a], x) >= 0) break;
                    heap[i] = heap[a];
                    i = a;
                }

                heap[i] = x;
                heap.RemoveAt(size);
                return ret;
            }

            private int Compare(T x, T y) => isAsc ? x.CompareTo(y) : y.CompareTo(x);
        }
    }

    static class Ex
    {
        public static Tuple<IEnumerable<T>, IEnumerable<T>> Split<T>(this IEnumerable<T> xs, Func<T, bool> f)
        {
            var ys = xs.Where(f);
            var zs = xs.Where(x => !f(x));
            return Tuple.Create(ys, zs);
        }

        public static void Iter<T>(this IEnumerable<T> xs, Action<T> f)
        {
            foreach (var x in xs) f(x);
        }

        public static void Prt<T>(this T x) => WriteLine(x);
        public static void Prt<T>(this IEnumerable<T> xs) => xs.Iter(x => WriteLine(x));

        public static void Log<T>(this T x)
        {
#if DEBUG
            WriteLine($"LOG [{nameof(x)}] : {x}");
#endif
        }

        public static IEnumerable<IndexedItem<T>> Indexed<T>(this IEnumerable<T> xs) =>
            xs.Select((x, idx) => new IndexedItem<T>(idx, x));

        public static IEnumerable<T> UnIndexed<T>(this IEnumerable<IndexedItem<T>> xs) => xs.Select(x => x.Val);

        public static IEnumerable<Tuple<T, T>> Pairwise<T>(this IEnumerable<T> xs) => ZIP(xs, xs.Skip(1));

        public static IEnumerable<int> ToZeroIndexed(this IEnumerable<int> xs) => xs.Select(x => x - 1);

        public static string Join<T>(this IEnumerable<T> xs, string str = " ") => String.Join(str, xs);

        public static string Sort(this string s)
        {
            var arr = s.ToCharArray();
            Array.Sort(arr);
            return new string(arr);
        }
    }
}