Binary Search Tree: C Program to implement a Binary Search Tree and perform deletion, inorder traversal on it
Binary Search Tree
C Program to implement a Binary Search Tree and perform deletion, inorder traversal on it
#include <stdio.h>
#include <stdlib.h>
struct btnode
{
int value;
struct btnode *l;
struct btnode *r;
}*root = NULL, *temp = NULL, *t2, *t1;
void delete1();
void insert();
void delete();
void inorder(struct btnode *t);
void create();
void search(struct btnode *t);
void preorder(struct btnode *t);
void postorder(struct btnode *t);
void search1(struct btnode *t,int data);
int smallest(struct btnode *t);
int largest(struct btnode *t);
void main()
{
int ch;
printf("\nOPERATIONS ---");
printf("\n1 - Insert an element into tree\n");
printf("2 - Delete an element from the tree\n");
printf("3 - Inorder Traversal\n");
printf("4 - Preorder Traversal\n");
printf("5 - Postorder Traversal\n");
printf("6 - Exit\n");
while(1)
{
printf("\nEnter your choice : ");
scanf("%d", &ch);
switch (ch)
{
case 1:
insert();
break;
case 2:
delete();
break;
case 3:
inorder(root);
break;
case 4:
preorder(root);
break;
case 5:
postorder(root);
break;
case 6:
exit(0);
default :
printf("Wrong choice, Please enter correct choice ");
break;
}
}
}
//Insert a node in the tree
void insert()
{
create();
if (root == NULL)
root = temp;
else
search(root);
}
// To create a node
void create()
{
int data;
printf("Enter data of node to be inserted : ");
scanf("%d", &data);
temp = (struct btnode *)malloc(sizeof(struct btnode));
temp->value = data;
temp->l = temp->r = NULL;
}
//Function to search the appropriate position to insert the new node
void search(struct btnode *t)
{
if ((temp->value > t->value) && (t->r != NULL)) //value more than root node value insert at right
search(t->r);
else if ((temp->value > t->value) && (t->r == NULL))
t->r = temp;
else if ((temp->value < t->value) && (t->l != NULL)) //value less than root node value insert at left
search(t->l);
else if ((temp->value < t->value) && (t->l == NULL))
t->l = temp;
}
//recursive function to perform inorder traversal of tree
void inorder(struct btnode *t)
{
if (root == NULL)
{
printf("No elements in a tree to display");
return;
}
if (t->l != NULL)
inorder(t->l);
printf("%d -> ", t->value);
if (t->r != NULL)
inorder(t->r);
}
// To check for the deleted node
void delete()
{
int data;
if (root == NULL)
{
printf("No elements in a tree to delete");
return;
}
printf("Enter the data to be deleted : ");
scanf("%d", &data);
t1 = root;
t2 = root;
search1(root, data);
}
//To find the preorder traversal
void preorder(struct btnode *t)
{
if (root == NULL)
{
printf("No elements in a tree to display");
return;
}
printf("%d -> ", t->value);
if (t->l != NULL)
preorder(t->l);
if (t->r != NULL)
preorder(t->r);
}
//To find the postorder traversal
void postorder(struct btnode *t)
{
if (root == NULL)
{
printf("No elements in a tree to display ");
return;
}
if (t->l != NULL)
postorder(t->l);
if (t->r != NULL)
postorder(t->r);
printf("%d -> ", t->value);
}
///Search for the appropriate position to insert the new node
void search1(struct btnode *t, int data)
{
if ((data>t->value))
{
t1 = t;
search1(t->r, data);
}
else if ((data < t->value))
{
t1 = t;
search1(t->l, data);
}
else if ((data==t->value))
{
delete1(t);
}
}
//To delete a node
void delete1(struct btnode *t)
{
int k;
// To delete leaf node
if ((t->l == NULL) && (t->r == NULL))
{
if (t1->l == t)
{
t1->l = NULL;
}
else
{
t1->r = NULL;
}
t = NULL;
free(t);
return;
}
//To delete node having one left hand child
else if ((t->r == NULL))
{
if (t1 == t)
{
root = t->l;
t1 = root;
}
else if (t1->l == t)
{
t1->l = t->l;
}
else
{
t1->r = t->l;
}
t = NULL;
free(t);
return;
}
// To delete node having right hand child
else if (t->l == NULL)
{
if (t1 == t)
{
root = t->r;
t1 = root;
}
else if (t1->r == t)
t1->r = t->r;
else
t1->l = t->r;
t = NULL;
free(t);
return;
}
// To delete node having two child
else if ((t->l != NULL) && (t->r != NULL))
{
t2 = root;
if (t->r != NULL)
{
k = smallest(t->r);
}
else
{
k =largest(t->l);
}
search1(root, k);
t->value = k;
}
}
// To find the smallest element in the right sub tree
int smallest(struct btnode *t)
{
t2 = t;
if (t->l != NULL)
{
t2 = t;
return(smallest(t->l));
}
else
return (t->value);
}
// To find the largest element in the left sub tree
int largest(struct btnode *t)
{
if (t->r != NULL)
{
t2 = t;
return(largest(t->r));
}
else
return(t->value);
}
/*
OPERATIONS ---
1 - Insert an element into tree
2 - Delete an element from the tree
3 - Inorder Traversal
4 - Preorder Traversal
5 - Postorder Traversal
6 - Exit
Enter your choice : 1
Enter data of node to be inserted : 40
Enter your choice : 1
Enter data of node to be inserted : 20
Enter your choice : 1
Enter data of node to be inserted : 10
Enter your choice : 1
Enter data of node to be inserted : 30
Enter your choice : 1
Enter data of node to be inserted : 60
Enter your choice : 1
Enter data of node to be inserted : 80
Enter your choice : 1
Enter data of node to be inserted : 90
Enter your choice : 3
10 -> 20 -> 30 -> 40 -> 60 -> 80 -> 90 ->
40
/\
/ \
20 60
/ \ \
10 30 80
\
90
*/
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