Find sum of all nodes of the given perfect binary tree

/*
    C Program 
    Find sum of all nodes of the given perfect binary tree
    Recursive solution
*/

#include <stdio.h>
#include <stdlib.h>

//Binary Tree node
struct Node
{
	int data;
	struct Node *left, *right;
};

//This is creating a binary tree node and return this
struct Node *get_node(int data)
{
	// Create dynamic node
	struct Node *new_node = (struct Node *) malloc(sizeof(struct Node));
	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");
	}
	//return new node
	return new_node;
}
//Display pre order elements
void preorder(struct Node *node)
{
	if (node != NULL)
	{
		//Print node value
		printf("  %d", node->data);
		preorder(node->left);
		preorder(node->right);
	}
}

//Calculate min depth of binary tree
int min_depth(struct Node *node)
{
	if (node == NULL)
	{
		return 0;
	}
	// Recursively, Finding the min height of nodes
	int a = min_depth(node->left);
	int b = min_depth(node->right);
	if (a > b)
	{
		return b + 1;
	}
	else
	{
		return a + 1;
	}
}

//Returns the sum of all nodes which are less than or equal to given level
int level_sum(struct Node *node, int k, int level)
{
	if (node == NULL)
	{
		return 0;
	}
	if (k <= level)
	{
		// Calculate node sum
		return node->data + level_sum(node->left, k + 1, level) + level_sum(node->right, k + 1, level);
	}
	else
	{
		return 0;
	}
}

//Find the sum of nodes of binary tree which is perfect binary tree
int perfect_binary_tree_sum(struct Node *root)
{
	if (root == NULL)
	{
		printf("\n Empty Binary Tree \n");
		return 0;
	}
	//First find min depth in binary tree
	int level = min_depth(root);
	//It return sum of nodes which are exist in root to min depth
	return level_sum(root, 1, level);
}

int main()
{
	struct Node *root = NULL;
	/*
	constructor binary tree
	-----------------------

	      6 
	    /   \                           
	   /     \    
	  7       3     
	 / \     /  \               
	8   10  2    1
	   /  \     / \
	  1    1   4   5
	      /
	     9
	-----------------------
	*/
	root = get_node(6);
	root->left = get_node(7);
	root->left->left = get_node(8);
	root->left->right = get_node(10);
	root->left->right->right = get_node(1);
	root->left->right->right->left = get_node(9);
	root->left->right->left = get_node(1);
	root->right = get_node(3);
	root->right->left = get_node(2);
	root->right->right = get_node(1);
	root->right->right->right = get_node(5);
	root->right->right->left = get_node(4);
	//Display Tree Element
	printf("\n Tree Nodes : ");
	preorder(root);
	/*
	Perfect form of above binary tree
	-----------------------

	      6 
	    /   \                           
	   /     \    
	  7       3     
	 / \     /  \               
	8   10  2    1

	-----------------------
	*/
	//Display Calculated Result
	printf("\n Perfect binary tree sum :  %d \n", perfect_binary_tree_sum(root));
	return 0;
}

Output

 Tree Nodes :   6  7  8  10  1  1  9  3  2  1  4  5
 Perfect binary tree sum :  37