Thread: Why does my BST program crash when I try to delete a node having grand children?

Code:

struct node
{
int data;
struct node *left, *right;
};
struct node *root=NULL;
int main()
{
root=insert(root,100);
insert(root,80);
insert(root,10);
insert(root,40);
insert(root,90);
insert(root,30);
insert(root,120);
insert(root,140);
inorder(root);
printf("Min: %d Max: %d\n", FindMin(root), FindMax(root)); 
delete(root,80);
printf("After deletion:\n");
inorder(root);
return 0;
}
struct node *insert(struct node *node, int data)
{
if(node==NULL)
{
return newnode(data);
}
else if(data < node->data)
{
node->left=insert(node->left, data);
}
else if(data > node->data)
{
node->right=insert(node->right,data);
}
return node;
}
struct node *newnode(int data)
{
struct node *tmp=(struct node*)malloc(sizeof(struct node));
tmp->data=data;
tmp->left=tmp->right=NULL;
return tmp;
}
struct node *inorder(struct node *root)
{
if(root!=NULL)
{
inorder(root->left);
printf("%d\n",root->data);
inorder(root->right); 
}
}
struct node *FindMin(struct node *root)
{
if(root==NULL)
{
printf("Tree is empty!\n");
return -1;
}
while(root->left!=NULL)
{
root=root->left;
}
return root->data;
}
struct node *FindMax(struct node *root)
{
if(root==NULL)
{
printf("Tree is empty!\n");
return -1;
}
while(root->right!=NULL)
{
root=root->right;
}
return root->data;
}
struct node *delete(struct node *root, int data)
{
if(root==NULL)
{
printf("Tree is empty!\n");
return -1;
}
else if(data < root->data)
{
root->left=delete(root->left, data);
}
else if(data > root->data)
{
root->right=delete(root->right, data);
}
else
{
if(root->left==NULL && root->right==NULL)
{
free(root);
root=NULL;
}
else if(root->left==NULL)
{
struct node *tmp=root;
// tmp=root;
root=root->right;
free(tmp);
}
else if(root->right==NULL)
{
struct node *tmp=root;
// tmp=root;
root=root->left;
free(tmp);
}
else
{
struct node *tmp=FindMin(root->right);
root->data=tmp->data;
root->right=delete(root->right,tmp->data);
}
}
return root;
}

Well, i found the problem. FindMin and Findmax functions need to return root only. No casting necessary unless you are going to print max and min values.