C - Binary Search Tree, delete node - c

Question

I have a question about my Code. "delete_single_node" does not work as it should. My procedure (to delete a node) is to find the node in the "head" tree, save the child nodes temporary, delete the node and all child nodes (in "head" tree) and merge the "head" tree with the temporary saved child nodes to a new correct binary tree.
I would like to stay with this procedure but I can't find my mistake.
#include <stdio.h>
#include <ctype.h>
#include <stdlib.h>
struct tnode {
int content;
struct tnode *left;
struct tnode *right;
};
struct tnode* head;
void *malloc(size_t size);
struct tnode *talloc(void)
{
return(struct tnode*)malloc(sizeof(struct tnode));
}
/* delete a node with all child nodes*/
int deletenode(struct tnode *p)
{
if (p == NULL) return 0;
else
{
deletenode(p->left);
deletenode(p->right);
p->left = NULL;
p->right = NULL;
free(p);
return 0;
}
}
/* insert new node*/
struct tnode *addelement(struct tnode *p, int i) {
int cond;
if (p == NULL) {
p = talloc();
p->content = i;
p->left = p->right = NULL;
}
else if (p->content == i) {
return p;
}
else if (i < p->content)
p->left = addelement(p->left, i);
else
p->right = addelement(p->right, i);
return p;
}
/*merges two binary trees into one*/
struct tnode *addtree(struct tnode *top, struct tnode *p) {
if (p == NULL)
return top;
else
return addtree(addtree(addelement(top, p->content), p->right), p->left);
}
/*prints out tree*/
void showtree(struct tnode* nd)
{
if (nd == NULL)
return;
printf("ZZ %d", nd->content);
if (nd->left != NULL)
{
printf("left:%d", nd->left->content);
}
if (nd->right != NULL)
{
printf("right:%d\n", nd->right->content);
}
printf("\n");
showtree(nd->left);
showtree(nd->right);
}
/*removes connection to a node*/
void removeconnection(struct tnode *head, struct tnode *p) {
if (p->content > head->content) {
if (head->right == p)
{
head->right = NULL;
}
else
{
removeconnection(head->right, p);
}
}
if (p->content < head->content) {
if (head->left == p)
{
head->left = NULL;
}
else
{
removeconnection(head->left, p);
}
}
}
/*delete single node*/
struct tnode *delete_single_node(struct tnode *p, int content) {
struct tnode* temp2 = NULL;
struct tnode temp1;
struct tnode* temp4 = NULL;
struct tnode temp3;
if (p == NULL)
return NULL;
if (content > p->content)
{
p->right = delete_single_node(p->right, content);
}
else if (content < p->content)
{
p->left = delete_single_node(p->left, content);
}
else if (content == p->content)
{
if (p->left == NULL && p->right != NULL)
{
temp1.content = p->right->content;
temp1.right = p->right->right;
temp1.left = p->right->left;
temp2 = &temp1;
removeconnection(head, p);
deletenode(p);
head = addtree(head, temp2);
showtree(head);
}
else if (p->right == NULL && p->left != NULL)
{
temp1.content = p->left->content;
temp1.right = p->left->right;
temp1.left = p->left->left;
temp2 = &temp1;
removeconnection(head, p);
deletenode(p);
head = addtree(head, temp2);
showtree(head);
}
else if (p->right == NULL && p->left == NULL)
{
removeconnection(head, p);
deletenode(p);
showtree(head);
}
else
{
temp1.content = p->left->content;
temp1.right = p->left->right;
temp1.left = p->left->left;
temp2 = &temp1;
temp3.content = p->right->content;
temp3.right = p->right->right;
temp3.left = p->right->left;
temp4 = &temp3;
removeconnection(head, p);
deletenode(p);
head = addtree(head, temp2);
head = addtree(head, temp4);
showtree(head);
}
}
}
int main()
{
struct tnode* start = NULL;
int temp_int;
start = addelement(start, 5);
start = addelement(start, 6);
start = addelement(start, 2);
start = addelement(start, 9);
start = addelement(start, 3);
start = addelement(start, 2);
start = addelement(start, 1);
start = addelement(start, 7);
start = addelement(start, 8);
showtree(start);
printf("Which node to delete?\n");
scanf_s("%d", &temp_int);
head = start;
delete_single_node(start, temp_int);
return 0;
}