avl.c

#include<stdio.h>
#include<stdlib.h>
struct Node
{
    int key;
    struct Node *left;
    struct Node *right;
    int height;
};
int height(struct Node *N)
{
    if (N == NULL)
        return 0;
    return N->height;
}
int max(int a, int b)
{
    return (a > b)? a : b;
}
struct Node* newNode(int key)
{
    struct Node* node = (struct Node*)
                        malloc(sizeof(struct Node));
    node->key   = key;
    node->left   = NULL;
    node->right  = NULL;
    node->height = 1;  
    return(node);
}
struct Node *rightRotate(struct Node *y)
{
    struct Node *x = y->left;
    struct Node *T2 = x->right;
    x->right = y;
    y->left = T2;
    y->height = max(height(y->left),
                    height(y->right)) + 1;
    x->height = max(height(x->left),
                    height(x->right)) + 1;
    return x;
}
struct Node *leftRotate(struct Node *x)
{
    struct Node *y = x->right;
    struct Node *T2 = y->left;
    y->left = x;
    x->right = T2;
    x->height = max(height(x->left),   
                    height(x->right)) + 1;
    y->height = max(height(y->left),
                    height(y->right)) +1;
    return y;
}
int getBalance(struct Node *N)
{
    if (N == NULL)
        return 0;
    return height(N->left) - height(N->right);
}
struct Node* insert(struct Node* node, int key)
{
    if (node == NULL)
        return(newNode(key));
    if (key < node->key)
        node->left  = insert(node->left, key);
    else if (key > node->key)
        node->right = insert(node->right, key);
    else 
        return node;
    node->height = 1 + max(height(node->left),
                        height(node->right));
    int balance = getBalance(node);
    if (balance > 1 && key < node->left->key)
        return rightRotate(node);
    if (balance < -1 && key > node->right->key)
        return leftRotate(node);
    if (balance > 1 && key > node->left->key)
    {
        node->left =  leftRotate(node->left);
        return rightRotate(node);
    }
    if (balance < -1 && key < node->right->key)
    {
        node->right = rightRotate(node->right);
        return leftRotate(node);
    }
    return node;
}
struct Node * minValueNode(struct Node* node)
{
    struct Node* current = node;
    while (current->left != NULL)
        current = current->left;
    return current;
}
struct Node* deleteNode(struct Node* root, int key)
{
    if (root == NULL)
        return root;
    if ( key < root->key )
        root->left = deleteNode(root->left, key);
    else if( key > root->key )
        root->right = deleteNode(root->right, key);
    else
    {
        if( (root->left == NULL) || (root->right == NULL) )
        {
            struct Node *temp = root->left ? root->left :
                                             root->right;
            if (temp == NULL)
            {
                temp = root;
                root = NULL;
            }
            else 
                *root = *temp;
            free(temp);
        }
        else
        {
            struct Node* temp = minValueNode(root->right);
            root->key = temp->key;
            root->right = deleteNode(root->right, temp->key);
        }
    }
    if (root == NULL)
      return root;
    root->height = 1 + max(height(root->left),
                           height(root->right));
    int balance = getBalance(root);
    if (balance > 1 && getBalance(root->left) >= 0)
        return rightRotate(root);
    if (balance > 1 && getBalance(root->left) < 0)
    {
        root->left =  leftRotate(root->left);
        return rightRotate(root);
    }
    if (balance < -1 && getBalance(root->right) <= 0)
        return leftRotate(root);
    if (balance < -1 && getBalance(root->right) > 0)
    {
        root->right = rightRotate(root->right);
        return leftRotate(root);
    }
    return root;
}
void preOrder(struct Node *root)
{
    if(root != NULL)
    {
        printf("%d ", root->key);
        preOrder(root->left);
        preOrder(root->right);
    }
}
int main()
{
  struct Node *root = NULL;
  root = insert(root, 10);
  root = insert(root, 20);
  root = insert(root, 30);
  root = insert(root, 40);
  root = insert(root, 50);
  root = insert(root, 25);
  printf("Preorder traversal : \n");
  preOrder(root);
  root = deleteNode(root, 10);
  printf("\nafter deletion : \n");
  preOrder(root);
  return 0;
}