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Predecessor and Successor in Binary Search Tree geeksforgeeks

Adel Wageeh answered on May 15, 2022 Popularity 8/10 Helpfulness 1/10

answer Predecessor and Successor in Binary Search Tree geeksforgeeks

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Predecessor and Successor in Binary Search Tree geeksforgeeks

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// C++ program to find predecessor and successor in a BST
#include <iostream>
using namespace std;
 
// BST Node
struct Node
{
    int key;
    struct Node *left, *right;
};
 
// This function finds predecessor and successor of key in BST.
// It sets pre and suc as predecessor and successor respectively
void findPreSuc(Node* root, Node*& pre, Node*& suc, int key)
{
    // Base case
    if (root == NULL)  return ;
 
    // If key is present at root
    if (root->key == key)
    {
        // the maximum value in left subtree is predecessor
        if (root->left != NULL)
        {
            Node* tmp = root->left;
            while (tmp->right)
                tmp = tmp->right;
            pre = tmp ;
        }
 
        // the minimum value in right subtree is successor
        if (root->right != NULL)
        {
            Node* tmp = root->right ;
            while (tmp->left)
                tmp = tmp->left ;
            suc = tmp ;
        }
        return ;
    }
 
    // If key is smaller than root's key, go to left subtree
    if (root->key > key)
    {
        suc = root ;
        findPreSuc(root->left, pre, suc, key) ;
    }
    else // go to right subtree
    {
        pre = root ;
        findPreSuc(root->right, pre, suc, key) ;
    }
}
 
// A utility function to create a new BST node
Node *newNode(int item)
{
    Node *temp =  new Node;
    temp->key = item;
    temp->left = temp->right = NULL;
    return temp;
}
 
/* A utility function to insert a new node with given key in BST */
Node* insert(Node* node, int key)
{
    if (node == NULL) return newNode(key);
    if (key < node->key)
        node->left  = insert(node->left, key);
    else
        node->right = insert(node->right, key);
    return node;
}
 
// Driver program to test above function
int main()
{
    int key = 65;    //Key to be searched in BST
 
   /* Let us create following BST
              50
           /     \
          30      70
         /  \    /  \
       20   40  60   80 */
    Node *root = NULL;
    root = insert(root, 50);
    insert(root, 30);
    insert(root, 20);
    insert(root, 40);
    insert(root, 70);
    insert(root, 60);
    insert(root, 80);
 
 
    Node* pre = NULL, *suc = NULL;
 
    findPreSuc(root, pre, suc, key);
    if (pre != NULL)
      cout << "Predecessor is " << pre->key << endl;
    else
      cout << "No Predecessor";
 
    if (suc != NULL)
      cout << "Successor is " << suc->key;
    else
      cout << "No Successor";
    return 0;
}

Popularity 8/10 Helpfulness 1/10 Language whatever

Source: www.geeksforgeeks.org

Tags: binary-search-tree whatever

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Contributed on May 15 2022

Adel Wageeh

0 Answers Avg Quality 2/10

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Predecessor and Successor in Binary Search Tree geeksforgeeks

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Input: root node, key
output: predecessor node, successor node

1. If root is NULL
      then return
2. if key is found then
    a. If its left subtree is not null
        Then predecessor will be the right most 
        child of left subtree or left child itself.
    b. If its right subtree is not null
        The successor will be the left most child 
        of right subtree or right child itself.
    return
3. If key is smaller then root node
        set the successor as root
        search recursively into left subtree
    else
        set the predecessor as root
        search recursively into right subtree

Popularity 9/10 Helpfulness 1/10 Language whatever

Source: www.geeksforgeeks.org

Tags: binary-search-tree whatever whatev

Link to this answer
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Contributed on May 15 2022

Adel Wageeh

0 Answers Avg Quality 2/10

Predecessor and Successor in Binary Search Tree geeksforgeeks

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