Using pointers with binary trees [duplicate] - c

Question

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Closed 10 years ago.
Possible Duplicate:
Binary tree - Dereferencing pointers
I was just trying to write a simple binary search tree program where the user can insert nodes and view all the nodes in the tree in either inorder,preorder or postorder mode. My code is
#include <stdio.h>
#include <stdlib.h>
struct treenode
{
int data;
struct treenode *lchild;
struct treenode *rchild;
};
void insertnode(struct treenode **n,int d)
{
struct treenode *p=&n;
if(p==NULL)
{
// means the tree is empty
p=(struct treenode *)malloc(sizeof(struct treenode));
p->data=d;
p->lchild=NULL;
p->rchild=NULL;
}
else
{
// strat comparing the new data from root
if( d<p->data )
insertnode(((p->lchild)),d);
else
insertnode(((p->rchild)),d);
}
}
void preorder(struct treenode **n)
{
struct treenode *p=&n;
if(p==NULL)
{
printf("\nThe list is empty");
}
else
{
printf("%d",p->data);
preorder(p->lchild);
preorder(p->rchild);
}
}
void postorder(struct treenode **n)
{
struct treenode *p=&n;
if(p==NULL)
{
printf("\nThe list is empty");
}
else
{
preorder(p->lchild);
preorder(p->rchild);
printf("%d",p->data);
}
}
void inorder(struct treenode **n)
{
struct treenode *p=&n;
if(p==NULL)
{
printf("\nThe list is empty");
}
else
{
preorder(p->lchild);
printf("%d",p->data);
preorder(p->rchild);
}
}
int main(void)
{
struct treenode *root=NULL;
int choice,data;
while(1)
{
printf("\nPress 1 for inserting a node in BST fashion: ");
printf("\nPress 2 for traversing the tree in preorder fashion :");
printf("\nPress 3 for traversing the tree in postorder fashion :");
printf("\nPress 4 for traversing the tree in inorder fashion :");
printf("\nPress 5 to exit :");
printf("\nEnter your choice: ");
scanf("%d", &choice);
switch(choice)
{
case 1: printf("\nEnter the data to be inserted:");
scanf("%d",&data);
insertnode(&root,data);
break;
case 2: preorder(&root);
break;
case 3: postorder(&root);
break;
case 4: inorder(&root);
break;
case 5: exit(0);
break;
default: printf("\nYou have enetred an invalid choice. Please try again");
}
}
return 0;
}
The program runs successfully, however after i have entered the node, the explorer detects an error and the program stops working. Is there any bug in the code ?

Answer 1

Spoiler:
#include <stdio.h>
#include <stdlib.h>
struct treenode {
struct treenode *lchild;
struct treenode *rchild;
int data;
} *root = NULL;
void insertnode(struct treenode **pp,int d)
{
for( ;*pp; )
{
if (d < (*pp)->data) pp = &(*pp)->lchild;
else pp = &(*pp)->rchild;
}
*pp = malloc (sizeof **pp);
(*pp)->data = d;
(*pp)->lchild = NULL;
(*pp)->rchild = NULL;
}
void preorder(struct treenode *p)
{
if(p==NULL)
{
printf("\nThe list is empty");
return;
}
printf("%d,",p->data);
if (p->lchild) preorder(p->lchild);
if (p->rchild) preorder(p->rchild);
}
void postorder(struct treenode *p)
{
if(p==NULL)
{
printf("\nThe list is empty");
return;
}
if (p->lchild) preorder(p->lchild);
if (p->rchild) preorder(p->rchild);
printf("%d,",p->data);
}
void inorder(struct treenode *p)
{
if(p==NULL)
{
printf("\nThe list is empty");
return;
}
if (p->lchild) preorder(p->lchild);
printf("%d,",p->data);
if (p->rchild) preorder(p->rchild);
}
int main(void)
{
root=NULL;
int choice,data;
while(1)
{
printf("\nPress 1 for inserting a node in BST fashion: ");
printf("\nPress 2 for traversing the tree in preorder fashion :");
printf("\nPress 3 for traversing the tree in postorder fashion :");
printf("\nPress 4 for traversing the tree in inorder fashion :");
printf("\nPress 5 to exit :");
printf("\nEnter your choice: ");
scanf("%d", &choice);
switch(choice)
{
case 1: printf("\nEnter the data to be inserted:");
scanf("%d",&data);
insertnode( &root,data);
break;
case 2: preorder(root);
break;
case 3: postorder(root);
break;
case 4: inorder(root);
break;
case 5: exit(0);
break;
default: printf("\nYou have entered an invalid choice. Please try again");
}
}
return 0;
}