Construct Tree From Given Inorder and Preorder traversals in C++

Construct Tree From Given Inorder and Preorder traversals in C++

There are three types of traversals in a tree: Inorder, Preorder and Postorder traversal. A tree can be formed with any two tree traversals in which one of them being the in order traversal. In this article, we will learn how to construct a tree from given inorder and preorder traversals in C++.

Construct tree from given inorder and preorder tree traversals in C++

Algorithm For InOrder Traversal:

  1. Traverse The Left subtree.
  2. Print the node.
  3. Traverse the right subtree.

Algorithm For PreOrder Traversal:

  1. Print the node.
  2. Traverse the left subtree.
  3. Traverse the right subtree.
Tree From Given Inorder And Preorder Traversals

Algorithm To Create Tree:

  1. Pick the first element and increment the count.
  2. Find the position of the element in inorder traversal.
  3. Call recursively for the left subtree and make it as the left child of the current node.
  4. Call recursively for the right subtree and make it as the right child of the current node.

Code Implementation for constructing tree from preorder and inorder traversals in C++

Run
#include<bits/stdc++.h>
using namespace std;
class Tree
{
public:
  int data;
  Tree *left = NULL, *right = NULL;
    Tree (int x)
  {
    data = x;
    left = NULL;
    right = NULL;
  }
};
int search (int inorder[], int start, int end, int element)
{
  int i = 0;
  for (i = start; i < end; i++)
    {
      if (inorder[i] == element)
	{
	  break;
	}
    }
  return i;
}

void printInorder (Tree * node)
{
  if (node == NULL)
    return;
  printInorder (node->left);
  cout << node->data << " ";
  printInorder (node->right);
}

Tree * build_tree (int inorder[], int preorder[], int start, int end)
{
  static int index = 0;
  if (start > end)
    return NULL;
  Tree *curr_node = new Tree (preorder[index++]);
  int x = curr_node->data;
  if (start == end)
    return curr_node;

  int search_index = search (inorder, start, end, x);

  curr_node->left = build_tree (inorder, preorder, start, search_index - 1);

  curr_node->right = build_tree (inorder, preorder, search_index + 1, end);

  return curr_node;
}

int main ()
{
  int in[] = { 12, 25, 30, 37, 40, 50, 60, 62, 70, 75, 87 };
  int pre[] = { 50, 25, 12, 37, 30, 40, 75, 62, 60, 70, 87 };
  Tree *root = build_tree (in, pre, 0, 10);
  cout << "Inorder traversal\n";
  printInorder (root);
  return 0;
}

Output:

Inorder traversal
12 25 30 37 40 50 60 62 70 75 87

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Introduction to Trees

Binary Trees

Binary Search Trees

Traversals

  • Traversal in Trees
  • Tree Traversals: Breadth-First Search (BFS) : C | C++ | Java
  • Tree Traversals: Depth First Search (DFS) : C | C++ | Java
  • Construct a Binary Tree from Postorder and Inorder

B – Trees

AVL Trees

  • AVL Trees
    • AVL Trees: Introduction
    • AVL Tree Insertion : C | C++ | Java
    • AVL Tree Deletion : C | C++ | Java
    • Insertion in a Binary Tree (Level Order) – C | C++ | Java
    • Searching in Binary Tree – C | C++ | Java
    • Searching in a Binary Search Tree – C | C++ | Java

Complete Programs for Trees

  • Depth First Traversals – C | C++ | Java
  • Level Order Traversal – C | C++Java
  • Construct Tree from given Inorder and Preorder traversals – C | C++Java
  • Construct Tree from given Postorder and Inorder traversals – C | C++Java
  • Construct Tree from given Postorder and Preorder traversal – C | C++Java
  • Find size of the Binary tree – C | C++Java
  • Find the height of binary tree – C | C++Java
  • Find maximum in binary tree – C | C++Java
  • Check whether two tree are identical- CC++Java
  • Spiral Order traversal of Tree- CC++Java
  • Level Order Traversal Line by Line – C | C++Java
  • Hand shaking lemma and some Impotant Tree Properties.
  • Check If binary tree if Foldable or not.- CC++Java
  • check whether tree is Symmetric – C| C++Java.
  • Check for Children-Sum in Binary Tree- C|C++Java
  • Sum of all nodes in Binary Tree- CC++ | Java
  • Lowest Common Ancestor in Binary Tree- CC++ | Java

Introduction to Trees

Binary Trees

Binary Search Trees

Traversals

  • Traversal in Trees
  • Tree Traversals: Breadth-First Search (BFS) : C | C++ | Java
  • Tree Traversals: Depth First Search (DFS) : C | C++ | Java
  • Construct a Binary Tree from Postorder and Inorder

B – Trees

AVL Trees

  • AVL Trees
    • AVL Trees: Introduction
    • AVL Tree Insertion :  C | C++ | Java
    • AVL Tree Deletion : C | C++ | Java
    • Insertion in a Binary Tree (Level Order) – C | C++ | Java
    • Searching in Binary Tree – C | C++ | Java
    • Searching in a Binary Search Tree – C | C++ | Java

Complete Programs for Trees

  • Depth First Traversals – C | C++ | Java
  • Level Order Traversal – C | C++Java
  • Construct Tree from given Inorder and Preorder traversals – C | C++Java
  • Construct Tree from given Postorder and Inorder traversals – C | C++Java
  • Construct Tree from given Postorder and Preorder traversal – C | C++Java
  • Find size of the Binary tree – C | C++Java
  • Find the height of binary tree – C | C++Java
  • Find maximum in binary tree – C | C++Java
  • Check whether two tree are identical- CC++Java
  • Spiral Order traversal of Tree- CC++Java
  • Level Order Traversal LIne by Line – C | C++Java
  • Hand shaking lemma and some Impotant Tree Properties.
  • Check If binary tree if Foldable or not.- CC++Java
  • check whether tree is Symmetric  C| C++Java.
  • Check for Children-Sum in Binary Tree- C|C++Java
  • Sum of all nodes in Binary Tree- CC++ | Java
  • Lowest Common Ancestor in Binary Tree. CC++ | Java