Check if two trees are isomorphic or not

/*
    C program for
    Check if two trees are isomorphic 
*/
#include <stdio.h>

#include <stdlib.h>

// Tree Node
struct TreeNode
{
    int data;
    struct TreeNode *left;
    struct TreeNode *right;
};
// Binary Tree
struct BinaryTree
{
    struct TreeNode *root;
};
// Create new tree
struct BinaryTree *newTree()
{
    // Create dynamic node
    struct BinaryTree *tree = (struct BinaryTree *) malloc(sizeof(struct BinaryTree));
    if (tree != NULL)
    {
        tree->root = NULL;
    }
    else
    {
        printf("Memory Overflow to Create tree Tree\n");
    }
    //return new tree
    return tree;
}
// This is creates and returns the new binary tree node
struct TreeNode *newNode(int data)
{
    // Create dynamic node
    struct TreeNode *new_node = 
      (struct TreeNode *) malloc(sizeof(struct TreeNode));
    if (new_node != NULL)
    {
        //Set data and pointer values
        new_node->data = data;
        new_node->left = NULL;
        new_node->right = NULL;
    }
    else
    {
        //This is indicates, 
        // segmentation fault or memory overflow problem
        printf("Memory Overflow\n");
        exit(0);
    }
    //return new node
    return new_node;
}
int isIsomorphic(struct TreeNode *t1, struct TreeNode *t2)
{
    if (t1 == NULL && t2 == NULL)
    {
        // When both t1 and t2 is null
        return 1;
    }
    if ((t1 == NULL || t2 == NULL) || (t1->data != t2->data))
    {
        // When one tree t1 or t2 node is empty or
        // t1 and t2 node value not similar
        return 0;
    }
    // When t1 and t2 tree are similar
    // Or t1 and t2 child are flipped to each other
    return (isIsomorphic(t1->left, t2->left) && isIsomorphic(t1->right, t2->right)) || (isIsomorphic(t1->left, t2->right) && isIsomorphic(t1->right, t2->left));
}
int main(int argc, char
    const *argv[])
{
    struct BinaryTree *tree1 = newTree();
    struct BinaryTree *tree2 = newTree();
    struct BinaryTree *tree3 = newTree();
    struct BinaryTree *tree4 = newTree();
    /*
             1                            
           /   \    
          2     7    
         / \     \               
        6   3     8
        ------------
        Binary tree A
    */
    tree1->root = newNode(1);
    tree1->root->left = newNode(2);
    tree1->root->right = newNode(7);
    tree1->root->right->right = newNode(8);
    tree1->root->left->right = newNode(3);
    tree1->root->left->left = newNode(6);
    /*
             1                            
           /   \    
          7     2    
         /     / \               
        8     3   6
        ------------
        Binary tree B
    */
    tree2->root = newNode(1);
    tree2->root->left = newNode(7);
    tree2->root->right = newNode(2);
    tree2->root->right->right = newNode(6);
    tree2->root->right->left = newNode(3);
    tree2->root->left->left = newNode(8);
    /*
             1                            
           /   \    
          7     9    
         /     / \               
        8     3   6
        ------------
        Binary tree C
    */
    tree3->root = newNode(1);
    tree3->root->left = newNode(7);
    tree3->root->right = newNode(9);
    tree3->root->right->right = newNode(6);
    tree3->root->right->left = newNode(3);
    tree3->root->left->left = newNode(8);
    /*
             1                            
           /   \    
          2     7    
         / \     \               
        6   3     8
        ------------
        Binary tree D
    */
    tree4->root = newNode(1);
    tree4->root->left = newNode(2);
    tree4->root->right = newNode(7);
    tree4->root->right->right = newNode(8);
    tree4->root->left->right = newNode(3);
    tree4->root->left->left = newNode(6);
    if (isIsomorphic(tree1->root, tree2->root) == 1)
    {
        printf("\n Tree1 and Tree2 is isomorphic");
    }
    else
    {
        printf("\n Tree1 and Tree2 is not isomorphic");
    }
    if (isIsomorphic(tree1->root, tree3->root) == 1)
    {
        printf("\n Tree1 and Tree3 is isomorphic");
    }
    else
    {
        printf("\n Tree1 and Tree3 is not isomorphic");
    }
    if (isIsomorphic(tree2->root, tree4->root) == 1)
    {
        printf("\n Tree2 and Tree4 is isomorphic");
    }
    else
    {
        printf("\n Tree2 and Tree4 is not isomorphic");
    }
    return 0;
}

Output

 Tree1 and Tree2 is isomorphic
 Tree1 and Tree3 is not isomorphic
 Tree2 and Tree4 is isomorphic