In this program, we are going to share how to sort linked list to balanced BST. If you are a beginner and want to start learning the C programming, then keep your close attention in this tutorial as I am going to share how to sort linked list to balanced BST with the output.
We have designed this program for beginners for learning purpose. Copy below c program and execute it with c compiler to see the output of the program.
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#include<stdio.h> #include<stdlib.h> /* Link list node */ struct LNode { int data; struct LNode* next; }; /* A Binary Tree node */ struct TNode { int data; struct TNode* left; struct TNode* right; }; struct TNode* newNode(int data); int countLNodes(struct LNode *head); struct TNode* sortedListToBSTRecur(struct LNode **head_ref, int n); /* This function counts the number of nodes in Linked List and then calls sortedListToBSTRecur() to construct BST */ struct TNode* sortedListToBST(struct LNode *head) { /*Count the number of nodes in Linked List */ int n = countLNodes(head); /* Construct BST */ return sortedListToBSTRecur(&head, n); } /* The main function that constructs balanced BST and returns root of it. head_ref --> Pointer to pointer to head node of linked list n --> No. of nodes in Linked List */ struct TNode* sortedListToBSTRecur(struct LNode **head_ref, int n) { /* Base Case */ if (n <= 0) return NULL; /* Recursively construct the left subtree */ struct TNode *left = sortedListToBSTRecur(head_ref, n/2); /* Allocate memory for root, and link the above constructed left subtree with root */ struct TNode *root = newNode((*head_ref)->data); root->left = left; /* Change head pointer of Linked List for parent recursive calls */ *head_ref = (*head_ref)->next; /* Recursively construct the right subtree and link it with root The number of nodes in right subtree is total nodes - nodes in left subtree - 1 (for root) which is n-n/2-1*/ root->right = sortedListToBSTRecur(head_ref, n-n/2-1); return root; } int countLNodes(struct LNode *head) { int count = 0; struct LNode *temp = head; while(temp) { temp = temp->next; count++; } return count; } /* Function to insert a node at the beginging of the linked list */ void push(struct LNode** head_ref, int new_data) { /* allocate node */ struct LNode* new_node = (struct LNode*) malloc(sizeof(struct LNode)); /* put in the data */ new_node->data = new_data; /* link the old list off the new node */ new_node->next = (*head_ref); /* move the head to point to the new node */ (*head_ref) = new_node; } /* Function to print nodes in a given linked list */ void printList(struct LNode *node) { while(node!=NULL) { printf("%d ", node->data); node = node->next; } } /* Helper function that allocates a new node with the given data and NULL left and right pointers. */ struct TNode* newNode(int data) { struct TNode* node = (struct TNode*) malloc(sizeof(struct TNode)); node->data = data; node->left = NULL; node->right = NULL; return node; } /* A utility function to print preorder traversal of BST */ void preOrder(struct TNode* node) { if (node == NULL) return; printf("%d ", node->data); preOrder(node->left); preOrder(node->right); } /* Drier program to test above functions*/ int main() { /* Start with the empty list */ struct LNode* head = NULL; /* Let us create a sorted linked list to test the functions Created linked list will be 1->2->3->4->5->6->7 */ push(&head, 7); push(&head, 6); push(&head, 5); push(&head, 4); push(&head, 3); push(&head, 2); push(&head, 1); printf("\n Given Linked List "); printList(head); struct TNode *root = sortedListToBST(head); printf("\n PreOrder Traversal of constructed BST "); preOrder(root); return 0; } |
Given Linked List 1 2 3 4 5 6 7
PreOrder Traversal of constructed BST 4 2 1 3 6 5 7
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