Binary Search tree, node deletion crash - c

Question

I coded a Binary Search tree. Every function works just fine, but the "deletenode". This method is supposed to delete the node which *p is pointing at.
However if the node is a leaf it prints the tree without the node and crashes.
If the node is no leaf it doesnt even print the tree and crashes.
I dont see any possible way to recreate the problem in less code, because i dont know where the problem is supposed to be. I'm Sorry.
Maybe someone can load it up and see where the problem is, because im really desperate.
#include <stdio.h>
void *malloc(size_t size);
void free(void *ptr);
struct tnode {
int content;
struct tnode *left; /* left subtree */
struct tnode *right; /* right subtree */
};
struct tnode *talloc(void) /* reserves memory*/
{
return (struct tnode *) malloc(sizeof(struct tnode));
}
struct tnode *addelement(struct tnode *p, int i) /* addelement: adds new node */
{
int cond;
if(p == NULL) {
p = talloc(); /* make a new node */ p->content = i;
p->left = p->right = NULL;
} else if(p->content == i) {
return p;
} else if(i < p->content) /* goes to the left side */ p->left = addelement(p->left, i);
else /* goes to the right side */ p->right = addelement(p->right, i);
return p;
}
struct tnode *addtree(struct tnode *top, struct tnode *p) /* adds subtree to main tree*/
{
if(p == NULL)
return top;
else
return addtree(addtree(addelement(top, p->content), p->right), p->left);
}
int printtree_preorder(struct tnode *p) /* prints tree in preorder*/
{
if(p != NULL) {
printf("%d \n", p->content);
printtree_preorder(p->left);
printtree_preorder(p->right);
}
return 0;
}
int printtree_inorder(struct tnode *p) /* prints tree in inorder*/
{
if(p != NULL) {
printtree_inorder(p->left);
printf("%d \n", p->content);
printtree_inorder(p->right);
}
return 0;
}
int printtree_postorder(struct tnode *p) /* prints tree in postorder*/
{
if(p != NULL) {
printtree_postorder(p->left);
printtree_postorder(p->right);
printf("%d \n", p->content);
}
return 0;
}
struct tnode *searchnode(struct tnode *p, int nodtodelete) /* pointer is set on the node which is supposed to be deleted */
{
if(p == NULL) {
printf("Baum ist leer oder Element nicht vorhanden \n");
return 0;
}
if(p->content == nodtodelete) {
return p;
}
if(p->content < nodtodelete) {
return searchnode(p->right, nodtodelete);
}
if(p->content > nodtodelete) {
return searchnode(p->left, nodtodelete);
}
}
struct tnode *deletenode(struct tnode *p, struct tnode *pBaum) /* Is supposed to delete the node which the *p is pointing at */
{
if((p->left == NULL) && (p->right == NULL)) {
free(p);
printf("Ist Blatt \n");
return pBaum;
}
if((p->left == NULL) && (p->right != NULL)) {
struct tnode *rechterTeilbaum = p->right;
free(p);
pBaum = addtree(pBaum, rechterTeilbaum);
return pBaum;
}
if((p->right == NULL) && (p->left != NULL)) {
struct tnode *linkerTeilbaum = p->left;
free(p);
pBaum = addtree(pBaum, linkerTeilbaum);
return pBaum;
}
if((p->left != NULL) && (p->right != NULL)) {
struct tnode *rechterTeilbaum = p->right;
struct tnode *linkerTeilbaum = p->left;
free(p);
pBaum = addtree(pBaum, rechterTeilbaum);
pBaum = addtree(pBaum, linkerTeilbaum);
return pBaum;
}
}
int main() {
struct tnode *Baum = NULL;
struct tnode *tmpPos = NULL;
Baum = addelement(Baum, 10);
Baum = addelement(Baum, 30);
Baum = addelement(Baum, 20);
Baum = addelement(Baum, 35);
tmpPos = searchnode(Baum, 35);
if(tmpPos != 0) {
printf("Zu loeschendes Element: %d \n", tmpPos->content);
Baum = deletenode(tmpPos, Baum);
}
printf("Inorder Ausgabe\n");
printtree_inorder(Baum);
printf("Postorder Ausgabe\n");
printtree_postorder(Baum);
printf("Preorder Ausgabe\n");
printtree_preorder(Baum);
}

Answer 1

In the deletenode function, you aren't checking to see if p is NULL before you try to dereference it. Are you segfaulting?