GeeksforGeeks » Interview Questions
Amazon Banglore Online Written
(4 posts)-
You are given a function getInorderSuccessor which takes a BST (Binary Search Tree) as it's parameter. Every node has an extra pointer "next" , which is intialized to null, fill next with node pointers which represent Inorder Successor.
In a binary tree, inorder successor of a node is the next node in inorder traversal of the binary tree. Inorder successor is NULL for the last node in inorder traversal.
In BST, inorder successor of an input node can also be defined as the node with the smallest key greater than the key of input node. So, it is sometimes important to find next node in sorted orde
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Traverse the node in reverse Inorder and store the pointer to previously visited node
/* Set next of all descendents of p */ void connectRecur(struct node* p) { // Initialize next as NULL as the first visited node would be the righmost node static struct node *next = NULL; if(p) { connectRecur(p->right); p->next = next; next = p; connectRecur(p->left); } } -
Following is complete program to test it.
#include <stdio.h> #include <stdlib.h> struct node { int data; struct node *left; struct node *right; struct node *next; }; /* Set next of all descendents of p */ void connectRecur(struct node* p) { // Base case static struct node *next = NULL; if(p) { connectRecur(p->right); p->next = next; next = p; connectRecur(p->left); } } void print(struct node *root) { while(root) { printf("%d ", root->data); root = root->next; } } /* UTILITY FUNCTIONS */ /* Helper function that allocates a new node with the given data and NULL left and right pointers. */ struct node* newnode(int data) { struct node* node = (struct node*) malloc(sizeof(struct node)); node->data = data; node->left = NULL; node->right = NULL; node->next = NULL; return(node); } /* Driver program to test above functions*/ int main() { /* Constructed binary tree is 10 / \ 8 12 / 3 */ struct node *root = newnode(10); root->left = newnode(8); root->right = newnode(12); root->left->left = newnode(3); // Populates nextRight pointer in all nodes connectRecur(root); print(root->left->left); getchar(); return 0; } -
Following function is a variation of above that doesn't use static variable.
void connect(struct node *root) { struct node *next = NULL; connectRecur(root, &next); } /* Set next of all descendents of p */ void connectRecur(struct node* p, struct node **next_ref) { if(p) { connectRecur(p->right, next_ref); p->next = *next_ref; *next_ref = p; connectRecur(p->left, next_ref); } }
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