Sorted Linked List to Balanced BST in C++

This C++ Program demonstrates the implementation of Sorted Linked List to Balanced BST.

Here is source code of the C++ Program to demonstrate the implementation of Sorted Linked List to Balanced BST. The C++ program is successfully compiled and run on a Linux system. The program output is also shown below.

```
/* 
```

 * C++ Program to Implement Sorted Linked List into Balanced BST

```
 */
```
```
#include<iostream>
```
```
#include<cstdlib>
```
```
using namespace std;
```
```
 
```
```
/* 
```
```
 * Link list node 
```
```
 */
```
```
struct LNode
```
```
{
```
```
    int data;
```
```
    LNode* next;
```
```
};
```
```
 
```
```
/* 
```
```
 * A Binary Tree node 
```
```
 */
```
```
struct TNode
```
```
{
```
```
    int data;
```
```
    TNode* left;
```
```
    TNode* right;
```
```
};
```
```
 
```
```
 
```
```
TNode* newNode(int data);
```
```
int countLNodes(LNode *head);
```

TNode* sortedListToBSTRecur(LNode **head_ref, int n);

```
 
```
```
 
```
```
/* 
```

 * counts the number of nodes in Linked List

```
 */
```
```
TNode* sortedListToBST(LNode *head)
```
```
{
```
```
    int n = countLNodes(head);
```

    return sortedListToBSTRecur(&head, n);

```
}
```
```
 
```
```
/* 
```

 * constructs balanced BST and returns root of it.

```
 */
```

TNode* sortedListToBSTRecur(LNode **head_ref, int n)

```
{
```
```
    if (n <= 0)
```
```
        return NULL;
```

    TNode *left = sortedListToBSTRecur(head_ref, n / 2);

    TNode *root = newNode((*head_ref)->data);

```
    root->left = left;
```
```
    *head_ref = (*head_ref)->next;
```

    root->right = sortedListToBSTRecur(head_ref, n - n / 2 - 1);

```
    return root;
```
```
}
```
```
 
```
```
/* 
```

 * returns count of nodes in a given Linked List

```
 */
```
```
int countLNodes(LNode *head)
```
```
{
```
```
    int count = 0;
```
```
    LNode *temp = head;
```
```
    while (temp)
```
```
    {
```
```
        temp = temp->next;
```
```
        count++;
```
```
    }
```
```
    return count;
```
```
}
```
```
 
```
```
/* 
```

 * insert a node at the beginging of the linked list

```
 */
```

void push(LNode** head_ref, int new_data)

```
{
```
```
    LNode* new_node = new LNode;
```
```
    new_node->data = new_data;
```
```
    new_node->next = (*head_ref);
```
```
    (*head_ref) = new_node;
```
```
}
```
```
 
```
```
/* 
```
```
 * print nodes in a given linked list
```
```
 */
```
```
void printList(LNode *node)
```
```
{
```
```
    while (node != NULL)
```
```
    {
```
```
        cout<<node->data<<"  ";
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```
        node = node->next;
```
```
    }
```
```
}
```
```
 
```
```
/* 
```

 * allocates a new node with the data and NULL left and right pointers.

```
 */
```
```
TNode* newNode(int data)
```
```
{
```
```
    TNode* node = new TNode;
```
```
    node->data = data;
```
```
    node->left = NULL;
```
```
    node->right = NULL;
```
```
    return node;
```
```
}
```
```
 
```
```
/* 
```
```
 * print preorder traversal of BST
```
```
 */
```
```
void preOrder(TNode* node)
```
```
{
```
```
    if (node == NULL)
```
```
        return;
```
```
    cout<<node->data<<"  ";
```
```
    preOrder(node->left);
```
```
    preOrder(node->right);
```
```
}
```
```
 
```
```
/* 
```
```
 * Main
```
```
 */
```
```
int main()
```
```
{
```
```
    LNode* head = NULL;
```
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    push(&head, 7);
```
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    push(&head, 6);
```
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    push(&head, 5);
```
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    push(&head, 4);
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    push(&head, 3);
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    push(&head, 2);
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    push(&head, 1);
```
```
    cout<<"\n Given Linked List ";
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```
    printList(head);
```

    TNode *root = sortedListToBST(head);

    cout<<"\n PreOrder Traversal of constructed BST ";

```
    preOrder(root);
```
```
    return 0;
```
```
}
```

$ g++ sorted_bst.cpp
$ a.out
 
 Given Linked List 1  2  3  4  5  6  7
 PreOrder Traversal of constructed BST 4  2  1  3  6  5  7
 
------------------
(program exited with code: 1)
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