TreeAndVertex

import java.util.*;

public class TreeAndVertex {
  static final int N = 100;

  boolean order(int l, int m, int r) {
    return l <= m && m <= r;
  }

  public String checkData(int[] tree) {
    int n = tree.length + 1;

    if (!order(2, n, 100))
      return "tree must contain between 1 and 99 elements, inclusive.";

    for (int i = 0; i < n - 1; ++i)
      if (!order(0, tree[i], i))
        return "tree[i] must be between 0 and i, inclusive.";

    return "";
  }

  public int get(int[] tree) {
    int n = tree.length + 1;
    Integer[] deg = new Integer[n];

    for (int i = 0; i < n; ++i)
      deg[i] = new Integer(0);

    for (int i = 0; i < n - 1; ++i) {
      deg[tree[i]]++;
      deg[i + 1]++;
    }

    return Collections.max(Arrays.asList(deg));
  }

  public static void main(String[] args) {
    TreeAndVertex solver = new TreeAndVertex();
    int[] tree = {0, 1, 2};
    System.out.println(solver.checkData(tree));
    System.out.println(solver.get(tree));
  }
};