DeadMen no Tales

Main.java

import java.io.OutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.List;
import java.util.InputMismatchException;
import java.io.IOException;
import java.io.InputStream;
import java.util.ArrayList;

/**
 * Built using CHelper plug-in Actual solution is at the top
 *
 * @author MaxHeap
 */
public class Main {

  public static void main(String[] args) {
    InputStream inputStream = System.in;
    OutputStream outputStream = System.out;
    InputReader in = new InputReader(inputStream);
    PrintWriter out = new PrintWriter(outputStream);
    DeadMenNotTales2 solver = new DeadMenNotTales2();
    solver.solve(1, in, out);
    out.close();
  }

  static class DeadMenNotTales2 {

    List<Integer>[] g;
    int n;
    int m;
    long[] sum;
    long[] count;

    void dfs(int u, int p) {
      count[u] = 1;
      for (int v : g[u]) {
        if (v != p) {
          dfs(v, u);
          sum[u] += sum[v] + count[v];
          count[u] += count[v];
        }
      }
    }

    void rec(int u, int p) {
      if (p != 0) {
        sum[u] = sum[p] + (count[p] - 2 * count[u]);
        count[u] = count[p];
      }
      for (int v : g[u]) {
        if (v != p) {
          rec(v, u);
        }
      }
    }

    public void solve(int testNumber, InputReader in, PrintWriter out) {
      n = in.nextInt();
      m = in.nextInt();
      sum = new long[n + 1];
      count = new long[n + 1];
      g = GraphUtils.generateGraph(n + 1);
      for (int i = 0; i < n - 1; i++) {
        int u = in.nextInt();
        int v = in.nextInt();
        g[u].add(v);
        g[v].add(u);
      }
      dfs(1, 0);
      rec(1, 0);
      long ans = ArrayUtils.sum(sum);
      out.println(ans / 2L);
    }

  }

  static class GraphUtils {

    private GraphUtils() {
    }

    public static List<Integer>[] generateGraph(int n) {
      List<Integer>[] graph = new ArrayList[n];
      for (int i = 0; i < n; i++) {
        graph[i] = new ArrayList<>();
      }
      return graph;
    }

  }

  static class ArrayUtils {

    public static long sum(long[] arr) {
      long ret = 0;
      for (int i = 0; i < arr.length; i++) {
        ret += arr[i];
      }
      return ret;
    }

  }

  static class InputReader {

    private InputStream stream;
    private byte[] buf = new byte[1 << 13];
    private int curChar;
    private int numChars;

    public InputReader(InputStream stream) {
      this.stream = stream;
    }

    public int read() {
      if (this.numChars == -1) {
        throw new UnknownError();
      } else {
        if (this.curChar >= this.numChars) {
          this.curChar = 0;

          try {
            this.numChars = this.stream.read(this.buf);
          } catch (IOException ex) {
            throw new InputMismatchException();
          }

          if (this.numChars <= 0) {
            return -1;
          }
        }

        return this.buf[this.curChar++];
      }
    }

    public int nextInt() {
      int c;
      for (c = this.read(); isSpaceChar(c); c = this.read()) {
      }

      byte sgn = 1;
      if (c == 45) {
        sgn = -1;
        c = this.read();
      }

      int res = 0;

      while (c >= 48 && c <= 57) {
        res *= 10;
        res += c - 48;
        c = this.read();
        if (isSpaceChar(c)) {
          return res * sgn;
        }
      }

      throw new InputMismatchException();
    }

    public static boolean isSpaceChar(int c) {
      return c == 32 || c == 10 || c == 13 || c == 9 || c == -1;
    }

  }
}