Replace each node in binary tree with the sum of its inorder predecessor and successor - GeeksforGeeks

25 Apr, 2022
Given a binary tree containing n nodes. The problem is to replace each node in the binary tree with the sum of its inorder predecessor and inorder successor.
Examples: 
Input :          1
               /   \
              2     3
            /  \  /  \
           4   5  6   7

Output :        11
              /    \
             9      13
            / \    /  \
           2   3   4   3
                  
For 1:
Inorder predecessor = 5
Inorder successor  = 6
Sum = 11

For 4:
Inorder predecessor = 0
(as inorder predecessor is not present)
Inorder successor  = 2
Sum = 2

For 7:
Inorder predecessor = 3
Inorder successor  = 0
(as inorder successor is not present)
Sum = 3
Approach: Create an array arr. Store 0 at index 0. Now, store the inorder traversal of tree in the array arr. Then, store 0 at last index. 0’s are stored as inorder predecessor of leftmost leaf and inorder successor of rightmost leaf is not present. Now, perform inorder traversal and while traversing node replace node’s value with arr[i-1] + arr[i+1] and then increment i. In the beginning initialize i = 1. For an element arr[i], the values arr[i-1] and arr[i+1] are its inorder predecessor and inorder successor respectively.
C++
Java
Python3
C#
Javascript
// C++ implementation to replace each node// in binary tree with the sum of its inorder// predecessor and successor#include <bits/stdc++.h> using namespace std; // node of a binary treestruct Node {    int data;    struct Node* left, *right;}; // function to get a new node of a binary treestruct Node* getNode(int data){    // allocate node    struct Node* new_node =       (struct Node*)malloc(sizeof(struct Node));     // put in the data;    new_node->data = data;    new_node->left = new_node->right = NULL;     return new_node;} // function to store the inorder traversal// of the binary tree in 'arr'void storeInorderTraversal(struct Node* root,                                vector<int>& arr){    // if root is NULL    if (!root)        return;     // first recur on left child    storeInorderTraversal(root->left, arr);     // then store the root's data in 'arr'    arr.push_back(root->data);     // now recur on right child    storeInorderTraversal(root->right, arr);} // function to replace each node with the sum of its// inorder predecessor and successorvoid replaceNodeWithSum(struct Node* root,                        vector<int> arr, int* i){    // if root is NULL    if (!root)        return;     // first recur on left child    replaceNodeWithSum(root->left, arr, i);     // replace node's data with the sum of its    // inorder predecessor and successor    root->data = arr[*i - 1] + arr[*i + 1];     // move 'i' to point to the next 'arr' element    ++*i;     // now recur on right child    replaceNodeWithSum(root->right, arr, i);} // Utility function to replace each node in binary// tree with the sum of its inorder predecessor// and successorvoid replaceNodeWithSumUtil(struct Node* root){    // if tree is empty    if (!root)        return;     vector<int> arr;     // store the value of inorder predecessor    // for the leftmost leaf    arr.push_back(0);     // store the inorder traversal of the tree in 'arr'    storeInorderTraversal(root, arr);     // store the value of inorder successor    // for the rightmost leaf    arr.push_back(0);      // replace each node with the required sum    int i = 1;    replaceNodeWithSum(root, arr, &i);} // function to print the preorder traversal// of a binary treevoid preorderTraversal(struct Node* root){    // if root is NULL    if (!root)        return;     // first print the data of node    cout << root->data << " ";     // then recur on left subtree    preorderTraversal(root->left);     // now recur on right subtree    preorderTraversal(root->right);} // Driver program to test aboveint main(){    // binary tree formation    struct Node* root = getNode(1); /*         1        */    root->left = getNode(2);        /*       /   \      */    root->right = getNode(3);       /*     2      3     */    root->left->left = getNode(4);  /*    /  \  /   \   */    root->left->right = getNode(5); /*   4   5  6   7   */    root->right->left = getNode(6);    root->right->right = getNode(7);     cout << "Preorder Traversal before tree modification:n";    preorderTraversal(root);     replaceNodeWithSumUtil(root);     cout << "\nPreorder Traversal after tree modification:n";    preorderTraversal(root);     return 0;}
// Java implementation to replace each node// in binary tree with the sum of its inorder// predecessor and successorimport java.util.*;class Solution{     // node of a binary treestatic class Node {    int data;     Node left, right;} //INT classstatic class INT{    int data;}  // function to get a new node of a binary treestatic  Node getNode(int data){    // allocate node     Node new_node =new Node();      // put in the data;    new_node.data = data;    new_node.left = new_node.right = null;      return new_node;}  // function to store the inorder traversal// of the binary tree in 'arr'static void storeInorderTraversal( Node root,                                Vector<Integer> arr){    // if root is null    if (root==null)        return;      // first recur on left child    storeInorderTraversal(root.left, arr);      // then store the root's data in 'arr'    arr.add(root.data);      // now recur on right child    storeInorderTraversal(root.right, arr);}  // function to replace each node with the sum of its// inorder predecessor and successorstatic void replaceNodeWithSum( Node root,                        Vector<Integer> arr, INT i){    // if root is null    if (root==null)        return;      // first recur on left child    replaceNodeWithSum(root.left, arr, i);      // replace node's data with the sum of its    // inorder predecessor and successor    root.data = arr.get(i.data - 1) + arr.get(i.data + 1);      // move 'i' to point to the next 'arr' element    i.data++;      // now recur on right child    replaceNodeWithSum(root.right, arr, i);}  // Utility function to replace each node in binary// tree with the sum of its inorder predecessor// and successorstatic void replaceNodeWithSumUtil( Node root){    // if tree is empty    if (root==null)        return;      Vector<Integer> arr= new Vector<Integer>();      // store the value of inorder predecessor    // for the leftmost leaf    arr.add(0);      // store the inorder traversal of the tree in 'arr'    storeInorderTraversal(root, arr);      // store the value of inorder successor    // for the rightmost leaf    arr.add(0);       // replace each node with the required sum    INT i = new INT();         i.data=1;         replaceNodeWithSum(root, arr, i);}  // function to print the preorder traversal// of a binary treestatic void preorderTraversal( Node root){    // if root is null    if (root==null)        return;      // first print the data of node    System.out.print( root.data + " ");      // then recur on left subtree    preorderTraversal(root.left);      // now recur on right subtree    preorderTraversal(root.right);}  // Driver program to test abovepublic static void main(String args[]){    // binary tree formation     Node root = getNode(1);       //         1           root.left = getNode(2);        //       /   \         root.right = getNode(3);       //     2      3        root.left.left = getNode(4);  //    /  \  /   \      root.left.right = getNode(5); //   4   5  6   7      root.right.left = getNode(6);    root.right.right = getNode(7);      System.out.println( "Preorder Traversal before tree modification:");    preorderTraversal(root);      replaceNodeWithSumUtil(root);      System.out.println("\nPreorder Traversal after tree modification:");    preorderTraversal(root);  }}//contributed by Arnab Kundu
# Python3 implementation to replace each# node in binary tree with the sum of its# inorder predecessor and successor # class to get a new node of a# binary treeclass getNode:    def __init__(self, data):                 # put in the data        self.data = data        self.left = self.right = None     # function to store the inorder traversal# of the binary tree in 'arr'def storeInorderTraversal(root, arr):         # if root is None    if (not root):        return     # first recur on left child    storeInorderTraversal(root.left, arr)     # then store the root's data in 'arr'    arr.append(root.data)     # now recur on right child    storeInorderTraversal(root.right, arr) # function to replace each node with the# sum of its inorder predecessor and successordef replaceNodeWithSum(root, arr, i):         # if root is None    if (not root):        return     # first recur on left child    replaceNodeWithSum(root.left, arr, i)     # replace node's data with the sum of its    # inorder predecessor and successor    root.data = arr[i[0] - 1] + arr[i[0] + 1]     # move 'i' to point to the next 'arr' element    i[0] += 1     # now recur on right child    replaceNodeWithSum(root.right, arr, i) # Utility function to replace each node in# binary tree with the sum of its inorder # predecessor and successordef replaceNodeWithSumUtil(root):         # if tree is empty    if (not root):        return     arr = []     # store the value of inorder predecessor    # for the leftmost leaf    arr.append(0)     # store the inorder traversal of the    # tree in 'arr'    storeInorderTraversal(root, arr)     # store the value of inorder successor    # for the rightmost leaf    arr.append(0)     # replace each node with the required sum    i = [1]    replaceNodeWithSum(root, arr, i) # function to print the preorder traversal# of a binary treedef preorderTraversal(root):         # if root is None    if (not root):        return     # first print the data of node    print(root.data, end = " ")     # then recur on left subtree    preorderTraversal(root.left)     # now recur on right subtree    preorderTraversal(root.right) # Driver Codeif __name__ == '__main__':         # binary tree formation    root = getNode(1) #         1        root.left = getNode(2)     #     / \        root.right = getNode(3)     #     2     3        root.left.left = getNode(4) # / \ / \    root.left.right = getNode(5) # 4 5 6 7    root.right.left = getNode(6)    root.right.right = getNode(7)     print("Preorder Traversal before",                 "tree modification:")    preorderTraversal(root)     replaceNodeWithSumUtil(root)    print()    print("Preorder Traversal after",                "tree modification:")    preorderTraversal(root) # This code is contributed by PranchalK
// C# implementation to replace each// node in binary tree with the sum// of its inorder predecessor and successorusing System;using System.Collections.Generic; class GFG{ // node of a binary treepublic class Node{    public int data;    public Node left, right;} // INT classpublic class INT{    public int data;} // function to get a new node// of a binary treepublic static Node getNode(int data){    // allocate node    Node new_node = new Node();     // put in the data;    new_node.data = data;    new_node.left = new_node.right = null;     return new_node;} // function to store the inorder traversal// of the binary tree in 'arr'public static void storeInorderTraversal(Node root,                                         List<int> arr){    // if root is null    if (root == null)    {        return;    }     // first recur on left child    storeInorderTraversal(root.left, arr);     // then store the root's data in 'arr'    arr.Add(root.data);     // now recur on right child    storeInorderTraversal(root.right, arr);} // function to replace each node with// the sum of its inorder predecessor// and successorpublic static void replaceNodeWithSum(Node root,                                      List<int> arr, INT i){    // if root is null    if (root == null)    {        return;    }     // first recur on left child    replaceNodeWithSum(root.left, arr, i);     // replace node's data with the    // sum of its inorder predecessor    // and successor    root.data = arr[i.data - 1] + arr[i.data + 1];     // move 'i' to point to the    // next 'arr' element    i.data++;     // now recur on right child    replaceNodeWithSum(root.right, arr, i);} // Utility function to replace each// node in binary tree with the sum// of its inorder predecessor and successorpublic static void replaceNodeWithSumUtil(Node root){    // if tree is empty    if (root == null)    {        return;    }     List<int> arr = new List<int>();     // store the value of inorder    // predecessor for the leftmost leaf    arr.Add(0);     // store the inorder traversal    // of the tree in 'arr'    storeInorderTraversal(root, arr);     // store the value of inorder successor    // for the rightmost leaf    arr.Add(0);     // replace each node with    // the required sum    INT i = new INT();     i.data = 1;     replaceNodeWithSum(root, arr, i);} // function to print the preorder// traversal of a binary treepublic static void preorderTraversal(Node root){    // if root is null    if (root == null)    {        return;    }     // first print the data of node    Console.Write(root.data + " ");     // then recur on left subtree    preorderTraversal(root.left);     // now recur on right subtree    preorderTraversal(root.right);} // Driver Codepublic static void Main(string[] args){    // binary tree formation    Node root = getNode(1); //         1    root.left = getNode(2); //     / \    root.right = getNode(3); //     2     3    root.left.left = getNode(4); // / \ / \    root.left.right = getNode(5); // 4 5 6 7    root.right.left = getNode(6);    root.right.right = getNode(7);     Console.WriteLine("Preorder Traversal " +                "before tree modification:");    preorderTraversal(root);     replaceNodeWithSumUtil(root);     Console.WriteLine("\nPreorder Traversal after " +                               "tree modification:");    preorderTraversal(root);}} // This code is contributed by Shrikant13
<script> // Javascript implementation to replace each node// in binary tree with the sum of its inorder// predecessor and successorclass Node{    constructor(data)    {        this.left = null;        this.right = null;        this.data = data;    }} // Function to get a new node of a// binary treefunction getNode(data){         // Allocate node    let new_node = new Node(data);    return new_node;} // Function to store the inorder traversal// of the binary tree in 'arr'function storeInorderTraversal(root, arr){         // If root is null    if (root == null)        return;     // First recur on left child    storeInorderTraversal(root.left, arr);     // then store the root's data in 'arr'    arr.push(root.data);     // Now recur on right child    storeInorderTraversal(root.right, arr);} // Function to replace each node with the// sum of its inorder predecessor and successorfunction replaceNodeWithSum(root, arr){         // If root is null    if (root == null)        return;     // First recur on left child    replaceNodeWithSum(root.left, arr);     // Replace node's data with the sum of its    // inorder predecessor and successor    root.data = arr[data - 1] + arr[data + 1];     // Move 'i' to point to the next 'arr' element    data++;     // Now recur on right child    replaceNodeWithSum(root.right, arr);} // Utility function to replace each node in binary// tree with the sum of its inorder predecessor// and successorfunction replaceNodeWithSumUtil(root){         // If tree is empty    if (root == null)        return;     let arr = [];     // Store the value of inorder predecessor    // for the leftmost leaf    arr.push(0);     // Store the inorder traversal of    // the tree in 'arr'    storeInorderTraversal(root, arr);     // Store the value of inorder successor    // for the rightmost leaf    arr.push(0);      // Replace each node with the required sum    data = 1;     replaceNodeWithSum(root, arr);} // Function to print the preorder traversal// of a binary treefunction preorderTraversal(root){         // If root is null    if (root == null)        return;     // First print the data of node    document.write(root.data + " ");     // Then recur on left subtree    preorderTraversal(root.left);     // Now recur on right subtree    preorderTraversal(root.right);} // Driver code // Binary tree formationlet root = getNode(1);       //           1       root.left = getNode(2);        //       /   \     root.right = getNode(3);       //     2      3    root.left.left = getNode(4);  //    /  \  /   \  root.left.right = getNode(5); //   4   5  6   7  root.right.left = getNode(6);root.right.right = getNode(7); document.write("Preorder Traversal before " +               "tree modification:" + "</br>");preorderTraversal(root); replaceNodeWithSumUtil(root); document.write("</br>" + "Preorder Traversal after " +               "tree modification:" + "</br>");preorderTraversal(root); // This code is contributed by divyeshrabadiya07 </script>
Preorder Traversal before tree modification:n1 2 4 5 3 6 7 
Preorder Traversal after tree modification:n11 9 2 3 13 4 3 
Output: 
Preorder Traversal before tree modification:
1 2 4 5 3 6 7
Preorder Traversal after tree modification:
11 9 2 3 13 4 3
Time Complexity: O(n) Auxiliary Space: O(n)
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Use inorder traversal and keep previous node and value of previous node’s  previous. 
Update previous node with current node + previous’s previous value  
C++
// C++ implementation to replace each node// in binary tree with the sum of its inorder// predecessor and successor#include <bits/stdc++.h>  using namespace std;  // node of a binary treestruct Node {    int data;    struct Node* left, *right;};  // function to get a new node of a binary treestruct Node* getNode(int data){    // allocate node    struct Node* new_node =       (struct Node*)malloc(sizeof(struct Node));      // put in the data;    new_node->data = data;    new_node->left = new_node->right = NULL;      return new_node;}   // function to print the preorder traversal// of a binary treevoid preorderTraversal(struct Node* root){    // if root is NULL    if (!root)        return;      // first print the data of node    cout << root->data << " ";      // then recur on left subtree    preorderTraversal(root->left);      // now recur on right subtree    preorderTraversal(root->right);} void inOrderTraverse(struct Node* root, struct Node* &prev, int &prevVal) {     if(root == NULL) return;     inOrderTraverse(root->left, prev, prevVal);     if(prev == NULL)     {         prev = root;         prevVal = 0;     }     else     {         int temp = prev->data;         prev->data = prevVal + root->data;         prev = root;         prevVal = temp;     }     inOrderTraverse(root->right, prev, prevVal); }// Driver program to test aboveint main(){    // binary tree formation    struct Node* root = getNode(1); /*         1        */    root->left = getNode(2);        /*       /   \      */    root->right = getNode(3);       /*     2      3     */    root->left->left = getNode(4);  /*    /  \  /   \   */    root->left->right = getNode(5); /*   4   5  6   7   */    root->right->left = getNode(6);    root->right->right = getNode(7);      cout << "Preorder Traversal before tree modification:\n";    preorderTraversal(root);    struct Node* prev = NULL;    int prevVal = -1;    inOrderTraverse(root, prev, prevVal);    // update righmost node.    prev->data = prevVal;      cout << "\nPreorder Traversal after tree modification:\n";    preorderTraversal(root);      return 0;}
Preorder Traversal before tree modification:
1 2 4 5 3 6 7 
Preorder Traversal after tree modification:
11 9 2 3 13 4 3 
Time Complexity: O(n) Auxiliary Space: O(n) due to recursive stack space  
andrew1234
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