text: AVL with duplicate keys | C ++ program of AVL tree that handles duplicates ; An AVL tree node ; A utility function to get maximum of two integers ; A utility function to get height of the tree ; A utility function to get maximum of two integers ; Helper function that allocates a new node with the given key and NULL left and right pointers . ; new node is initially added at leaf ; A utility function to right rotate subtree rooted with y See the diagram given above . ; Perform rotation ; Update heights ; Return new root ; A utility function to left rotate subtree rooted with x See the diagram given above . ; Perform rotation ; Update heights ; Return new root ; Get Balance factor of node N ; 1. Perform the normal BST rotation ; If key already exists in BST , increment count and return ; Otherwise , recur down the tree ; 2. Update height of this ancestor node ; 3. Get the balance factor of this ancestor node to check whether this node became unbalanced ; If this node becomes unbalanced , then there are 4 cases Left Left Case ; Right Right Case ; Left Right Case ; Right Left Case ; return the ( unchanged ) node pointer ; Given a non - empty binary search tree , return the node with minimum key value found in that tree . Note that the entire tree does not need to be searched . ; loop down to find the leftmost leaf ; STEP 1 : PERFORM STANDARD BST DELETE ; If the key to be deleted is smaller than the root 's key,  then it lies in left subtree ; If the key to be deleted is greater than the root 's key,  then it lies in right subtree ; if key is same as root 's key, then This is the node  to be deleted ; If key is present more than once , simply decrement count and return ; Else , delete the node node with only one child or no child ; No child case ; One child case ; Copy the contents of the non - empty child ; node with two children : Get the inorder successor ( smallest in the right subtree ) ; Copy the inorder successor 's data to this node and update the count ; Delete the inorder successor ; If the tree had only one node then return ; STEP 2 : UPDATE HEIGHT OF THE CURRENT NODE ; STEP 3 : GET THE BALANCE FACTOR OF THIS NODE ( to check whether this node became unbalanced ) ; If this node becomes unbalanced , then there are 4 cases Left Left Case ; Left Right Case ; Right Right Case ; Right Left Case ; A utility function to print preorder traversal of the tree . The function also prints height of every node ; Driver program to test above function ; Constructing tree given in the above figure
code: #include <stdio.h> NEW_LINE #include <stdlib.h> NEW_LINE struct node { int key ; struct node * left ; struct node * right ; int height ; int count ; } ; int max ( int a , int b ) ; 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 ; node -> count = 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 -> count ) ++ ; return node ; } if ( key < node -> key ) node -> left = insert ( node -> left , key ) ; else node -> right = insert ( node -> right , key ) ; node -> height = max ( height ( node -> left ) , height ( node -> right ) ) + 1 ; 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 -> count > 1 ) { ( root -> count ) -- ; return ; } 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 -> count = temp -> count ; temp -> count = 1 ; root -> right = deleteNode ( root -> right , temp -> key ) ; } } if ( root == NULL ) return root ; root -> height = max ( height ( root -> left ) , height ( root -> right ) ) + 1 ; 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 ( % d ) ▁ " , root -> key , root -> count ) ; preOrder ( root -> left ) ; preOrder ( root -> right ) ; } } int main ( ) { struct node * root = NULL ; root = insert ( root , 9 ) ; root = insert ( root , 5 ) ; root = insert ( root , 10 ) ; root = insert ( root , 5 ) ; root = insert ( root , 9 ) ; root = insert ( root , 7 ) ; root = insert ( root , 17 ) ; printf ( " Pre ▁ order ▁ traversal ▁ of ▁ the ▁ constructed ▁ AVL ▁ tree ▁ is ▁ STRNEWLINE " ) ; preOrder ( root ) ; root = deleteNode ( root , 9 ) ; printf ( " Pre order traversal after deletion of 9 " preOrder ( root ) ; return 0 ; }