Check for continuous binary tree in c

C program for Check for continuous binary tree. Here more information.

// Include header file
#include <stdio.h>
#include <stdlib.h>
/* 
  C program for
  Check if binary tree is continuous tree
  Using recursion
*/
// Binary Tree Node
typedef struct TreeNode
{
	// Define useful field of TreeNode
	int data;
	struct TreeNode * left;
	struct TreeNode * right;
}TreeNode;

TreeNode * getTreeNode(int data)
{
	// Create dynamic memory of TreeNode
	TreeNode * ref = (TreeNode * ) malloc(sizeof(TreeNode));
	if (ref == NULL)
	{
		// Failed to create memory 
		return NULL;
	}
	// Set node value
	ref->data = data;
	ref->left = NULL;
	ref->right = NULL;
	return ref;
}

typedef struct BinaryTree
{
	// Define useful field of BinaryTree
	struct TreeNode * root;
}BinaryTree;

BinaryTree * getBinaryTree()
{
	// Create dynamic memory of BinaryTree
	BinaryTree * ref = (BinaryTree * ) malloc(sizeof(BinaryTree));
	if (ref == NULL)
	{
		// Failed to create memory 
		return NULL;
	}
	// Set initial tree root
	ref->root = NULL;
	return ref;
}
int absValue(int num)
{
	if (num < 0)
	{
		return -num;
	}
	return num;
}
// Check tree is continuous or not
int isContinuous(TreeNode * node)
{
	if (node != NULL)
	{
		if ((node->left != NULL && 
            absValue(node->data - node->left->data) != 1) || 
            (node->right != NULL && 
             absValue(node->data - node->right->data) != 1))
		{
			// Case
			// When fail continuous tree rule
			return 0;
		}
		if (isContinuous(node->left) && 
            isContinuous(node->right))
		{
			return 1;
		}
		// When node value is not satisfied 
      	// continuous tree properties
		return 0;
	}
	return 1;
}
int main()
{
	// Create new tree
	BinaryTree * tree = getBinaryTree();
	/*  
	   Binary Tree
	   ------------
	       5
	     /   \
	    4     4
	   /     /  \
	  3     5    3
	   \
	    2
	        
	*/
	// Add tree node
	tree->root = getTreeNode(5);
	tree->root->left = getTreeNode(4);
	tree->root->right = getTreeNode(4);
	tree->root->left->left = getTreeNode(3);
	tree->root->right->right = getTreeNode(3);
	tree->root->right->left = getTreeNode(5);
	tree->root->left->left->right = getTreeNode(2);
	if (isContinuous(tree->root) == 1)
	{
		printf("Continuous Tree\n");
	}
	else
	{
		printf("Not Continuous Tree\n");
	}
	// Case 2
	/* 
	       5
	     /   \
	    4     4
	   /     /  \
	  3     5    3
	   \
	    1  <--- change value
	        
	*/
	tree->root->left->left->right->data = 1;
	if (isContinuous(tree->root) == 1)
	{
		printf("Continuous Tree\n");
	}
	else
	{
		printf("Not Continuous Tree\n");
	}
}

Output

Continuous Tree
Not Continuous Tree