Implementation binary search tree

c/Binary_tree.c

@@ -0,0 +1,288 @@
+/* 
+ * C Program to Construct 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);
+
+int flag = 1;
+
+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;    
+        }
+    }
+}
+
+/* To 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(1*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);
+            flag = 1;
+        }
+        else
+        {
+            k =largest(t->l);
+            flag = 2;
+        }
+        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);
+}