Tree ADT - Array Implementation

Tree Class
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using System;

namespace Tree_Adt_Array_Implementation
{
     class BinaryTree
     {
          private int [] tree;
          private int size;

          public BinaryTree(int size)
          {
               this.size = size;
               tree = new int[size + 1];
          }

          public void CreateBinaryTree()
          {
               for (int i = 1; i <= size; i++)
               {
                    Console.Write("Enter an integer : ");
                    tree[i] = int.Parse(Console.ReadLine());
               }
          }

          public int searchIndex(int value)
          {
               int i = 1;
               while (i <= size)
               {
                    if (value == tree[i])
                         return i;
                    i++;
               }
               return 0;

          }

          public int parent(int value)
          {
               int index;
               index = searchIndex(value);
               if (index == 0)
               {
                    Console.WriteLine("Node does not exist.");
                    return 0;
               }
               else
                    return tree[index / 2];
          }

          public int leftchild(int value)
          {
               int index;
               index = searchIndex(value);
               if (index == 0)
               {
                    Console.WriteLine("Node does not exist.");
                    return 0;
               }
               else
                    return tree[index * 2];
          }

          public int rightchild(int value)
          {
               int index;
               index = searchIndex(value);
               if (index == 0)
               {
                    Console.WriteLine("Node does not exist.");
                    return 0;
               }
               else
                    return tree[index * 2 + 1];
          }
     }
}








Driver Program Using Tree ADT
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using System;

namespace Tree_Adt_Array_Implementation
{
     class Program
     {
          static void Main(string[] args)
          {
               BinaryTree bt = new BinaryTree(7);
               bt.CreateBinaryTree(); //input: {20, 7, 25, 10, 15, 30, 22}
               Console.WriteLine("Left child of node 7 {0}",bt.leftchild(7)); //node 10
               Console.WriteLine("Right child of node 7 {0}", bt.rightchild(7)); //node 15
               Console.WriteLine("Parent of node 7 {0}", bt.parent(20)); // 20

               Console.ReadKey();
          }
     }
}