HackerRank: World codesprint #4 - Roads in HackerLand - study C# code

RoadsInHackerLand1.cs

using System;
using System.Collections.Generic;
using System.Globalization;
using System.IO;
using System.Linq;
using System.Text;
using System.Threading;

public class Solver
{
    class Dsu
    {
        private readonly int[] parent;

        public Dsu(int n)
        {
            parent = Enumerable.Range(0, n).ToArray();
        }

        public int FindSet(int v)
        {
            if (v == parent[v])
                return v;
            return parent[v] = FindSet(parent[v]);
        }

        public void UnionSets(int a, int b)
        {
            a = FindSet(a);
            b = FindSet(b);
            if (a != b)
                parent[b] = a;
        }
    }

    public void Solve()
    {
        int n = ReadInt();
        int m = ReadInt();

        var ed = ReadIntMatrix(m);
        Array.Sort(ed, (e1, e2) => e1[2].CompareTo(e2[2]));
        var dsu = new Dsu(n);
        var g = Init<List<Tuple<int, int>>>(n);
        for (int i = 0; i < m; i++)
        {
            ed[i][0]--;
            ed[i][1]--;
            if (dsu.FindSet(ed[i][0]) != dsu.FindSet(ed[i][1]))
            {
                g[ed[i][0]].Add(Tuple.Create(ed[i][1], ed[i][2]));
                g[ed[i][1]].Add(Tuple.Create(ed[i][0], ed[i][2]));
                dsu.UnionSets(ed[i][0], ed[i][1]);
            }
        }

        var stack = new Stack<Tuple<int, int>>();
        var stack2 = new Stack<Tuple<int, int>>();
        stack.Push(Tuple.Create(0, -1));
        while (stack.Count > 0)
        {
            var t = stack.Pop();
            foreach (var e in g[t.Item1])
                if (e.Item1 != t.Item2)
                    stack.Push(Tuple.Create(e.Item1, t.Item1));
            stack2.Push(t);
        }

        var cnt = new int[n];
        while (stack2.Count > 0)
        {
            var t = stack2.Pop();
            cnt[t.Item1] = 1;
            foreach (var e in g[t.Item1])
                if (e.Item1 != t.Item2)
                    cnt[t.Item1] += cnt[e.Item1];
        }

        var stack3 = new Stack<Tuple<int, int, int>>();
        var ans = Enumerable.Repeat(0L, m).ToList();
        stack3.Push(Tuple.Create(0, -1, 0));
        while (stack3.Count > 0)
        {
            var t = stack3.Pop();
            foreach (var e in g[t.Item1])
                if (e.Item1 != t.Item2)
                {
                    ans[e.Item2] = 1L * cnt[e.Item1] * (cnt[t.Item1] - cnt[e.Item1] + t.Item3);
                    stack3.Push(Tuple.Create(e.Item1, t.Item1, t.Item3 + cnt[t.Item1] - cnt[e.Item1]));
                }
        }

        for (int i = 0; i < ans.Count; i++)
        {
            long ex = ans[i] / 2;
            ans[i] %= 2;
            if (ex > 0)
            {
                if (i == ans.Count - 1)
                    ans.Add(0);
                ans[i + 1] += ex;
            }
        }
        while (ans[ans.Count - 1] == 0)
            ans.RemoveAt(ans.Count - 1);
        ans.Reverse();

        Write(string.Concat(ans));
    }

    #region Main

    protected static TextReader reader;
    protected static TextWriter writer;
    static void Main()
    {
#if DEBUG
        reader = new StreamReader("..\\..\\input.txt");
        //reader = new StreamReader(Console.OpenStandardInput());
        writer = Console.Out;
        //writer = new StreamWriter("..\\..\\output.txt");
#else
        reader = new StreamReader(Console.OpenStandardInput());
        writer = new StreamWriter(Console.OpenStandardOutput(),Encoding.ASCII);
        //reader = new StreamReader("input.txt");
        //writer = new StreamWriter("output.txt");
#endif
        try
        {
            new Solver().Solve();
            //var thread = new Thread(new Solver().Solve, 1024 * 1024 * 128);
            //thread.Start();
            //thread.Join();
        }
        catch (Exception ex)
        {
#if DEBUG
            Console.WriteLine(ex);
#else
            throw;
#endif
        }
        reader.Close();
        writer.Close();
    }

    #endregion

    #region Read / Write
    private static Queue<string> currentLineTokens = new Queue<string>();
    private static string[] ReadAndSplitLine() { return reader.ReadLine().Split(new[] { ' ', '\t', }, StringSplitOptions.RemoveEmptyEntries); }
    public static string ReadToken() { while (currentLineTokens.Count == 0)currentLineTokens = new Queue<string>(ReadAndSplitLine()); return currentLineTokens.Dequeue(); }
    public static int ReadInt() { return int.Parse(ReadToken()); }
    public static long ReadLong() { return long.Parse(ReadToken()); }
    public static double ReadDouble() { return double.Parse(ReadToken(), CultureInfo.InvariantCulture); }
    public static int[] ReadIntArray() { return ReadAndSplitLine().Select(int.Parse).ToArray(); }
    public static long[] ReadLongArray() { return ReadAndSplitLine().Select(long.Parse).ToArray(); }
    public static double[] ReadDoubleArray() { return ReadAndSplitLine().Select(s => double.Parse(s, CultureInfo.InvariantCulture)).ToArray(); }
    public static int[][] ReadIntMatrix(int numberOfRows) { int[][] matrix = new int[numberOfRows][]; for (int i = 0; i < numberOfRows; i++)matrix[i] = ReadIntArray(); return matrix; }
    public static int[][] ReadAndTransposeIntMatrix(int numberOfRows)
    {
        int[][] matrix = ReadIntMatrix(numberOfRows); int[][] ret = new int[matrix[0].Length][];
        for (int i = 0; i < ret.Length; i++) { ret[i] = new int[numberOfRows]; for (int j = 0; j < numberOfRows; j++)ret[i][j] = matrix[j][i]; } return ret;
    }
    public static string[] ReadLines(int quantity) { string[] lines = new string[quantity]; for (int i = 0; i < quantity; i++)lines[i] = reader.ReadLine().Trim(); return lines; }
    public static void WriteArray<T>(IEnumerable<T> array) { writer.WriteLine(string.Join(" ", array)); }
    public static void Write(params object[] array) { WriteArray(array); }
    public static void WriteLines<T>(IEnumerable<T> array) { foreach (var a in array)writer.WriteLine(a); }
    private class SDictionary<TKey, TValue> : Dictionary<TKey, TValue>
    {
        public new TValue this[TKey key]
        {
            get { return ContainsKey(key) ? base[key] : default(TValue); }
            set { base[key] = value; }
        }
    }
    private static T[] Init<T>(int size) where T : new() { var ret = new T[size]; for (int i = 0; i < size; i++)ret[i] = new T(); return ret; }
    #endregion
}