Find the sum of nodes in binary tree

#include <stdio.h>
#include <stdlib.h>
struct tree_node
{
	struct node *lchild;
	struct node *rchild;
	int data;
};
struct queue{
	int size;
	int front ; 
	int rear;
	struct tree_node **Q;
};
void create(struct queue *q,int size)
{
	q->size=size;
	q->front=q->rear=0;
	q->Q=(struct tree_node**)malloc(q->size*sizeof(struct tree_node *));
}
void enqueue(struct queue *q , struct tree_node *x)
{
	if((q->rear+1)%q->size == q->front)
	printf("Queue is Full\n");
	else
	{
		q->rear=(q->rear+1)%q->size;
		q->Q[q->rear]=x;
	}
}
struct tree_node * dequeue(struct queue *q )
{
	struct tree_node *x =  NULL;
	if(q->front==q->rear)
	printf("Queue is empty\n");
	else
	{
		q->front++;
		x = q->Q[q->front];
	}
	return x;
}

int isEmpty(struct queue q)
{
	return q.front==q.rear;
}

//Code For TREEEEE

struct tree_node *root = NULL;



int Tree_create(){
	struct tree_node *p,*t;;
	int sum=0;
	int x;
	struct queue q;
	create(&q,100);
	printf("enter the root value\n");
	scanf("%d",&x);
	root = (struct tree_node *)malloc(sizeof(struct tree_node *));
	root->data  = x;
	sum=sum+x;
	root->lchild = root->rchild=NULL;
	enqueue(&q,root);
	while(!isEmpty(q))
	{
		p=dequeue(&q);
		printf("Enter left child of %d\t",p->data);
		scanf("%d",&x);
		if(x!=-1)
		{
			t = (struct tree_node*)malloc(sizeof(struct tree_node ));
			t->data=x;
			sum=sum+x;
			(t->lchild)=(t->rchild)=NULL;
			(p->rchild)=t;
			enqueue(&q,t);
		}
		
		printf("Enter right child of %d\t",p->data);
		scanf("%d",&x);
		if(x!=-1)
		{
			t = (struct tree_node*)malloc(sizeof(struct tree_node ));
			t->data=x;
			sum=sum+x;
			(t->lchild)=(t->rchild)=NULL;
			(p->rchild)=t;
			enqueue(&q,t);
		}
	}
	return sum;
}
int main(int argc, char** argv) {
	int a;
	printf("----------------To Find Sum of nodes in tree--------------\n\n");
	printf("If you enter -1 in this code node for that particular will not be created futher\n\n\n");

	a= Tree_create();
	printf("Sum of all the root nodes is %d",a);
	return 0;
}