Replace every node with depth in N-ary Generic Tree

Given an array arr[] representing a Generic(N-ary) tree. The task is to replace the node data with the depth(level) of the node. Assume level of root to be 0.

Array Representation: The N-ary tree is serialized in the array arr[] using level order traversal as described below: 

• The input is given as a level order traversal of N-ary Tree.
• The first element of the array arr[] is the root node.
• Then, followed by a number N, which denotes the number of children of the previous node. Value zero denotes Null Node.

Examples:

Input: arr[] = { 10, 3, 20, 30, 40, 2, 40, 50, 0, 0, 0, 0 } 
Below is the N-ary Tree of the above array level order traversal: 

Output:
Below is the representation of the above output: 

Input: arr[] = {1, 3, 2, 3, 4, 2, 5, 6, 0, 0, 2, 8, 9} 
Below is the N-ary Tree of the above array level order traversal: 

Output:
Below is the representation of the above output: 

Approach:

• Traverse the tree starting from root.
• While traversing pass depth of node as a parameter.
• Track depth by passing it as 0 for root and (1 + current level) for children.

Below is the implementation of the above approach:

CPP

// C++ program to implement node with
// it's depth value
#include <bits/stdc++.h>
using namespace std;

// Treenode class using template
template <typename T>
class TreeNode {
public:
    // To store node value
    T data;

    // Pointer to TreeNode to store
    // the child node
    vector<TreeNode<T>*> children;

    // Constructor to assign data
    // to node
    TreeNode(T data)
    {
        this->data = data;
    }

    // Destructors to delete a node
    ~TreeNode()
    {
        for (int i = 0;
             i < children.size(); i++) {
            delete children[i];
        }
    }
};

// Function to take input level wise
// i.e., in level order traversal
TreeNode<int>* takeInputLevelWise(int arr[])
{
    int idx = 1;

    // Input root
    int rootData = arr[0];

    // Initialize tree with a root node
    TreeNode<int>* root
        = new TreeNode<int>(rootData);

    // Initialise queue for appending
    // node as a child of parent in
    // N-ary tree
    queue<TreeNode<int>*> pendingNodes;

    // Push the root node in queue
    pendingNodes.push(root);

    // While queue is not empty append
    // child to the root
    while (pendingNodes.size() != 0) {

        // Take the first node
        TreeNode<int>* front
            = pendingNodes.front();
        pendingNodes.pop();

        // Input number of child
        int numChild = arr[idx];
        idx++;

        for (int i = 0; i < numChild; i++) {

            int childData = arr[idx];
            idx++;

            // Make child Node
            TreeNode<int>* child
                = new TreeNode<int>(childData);

            // Append child node to
            // it's parent
            front->children.push_back(child);
            pendingNodes.push(child);
        }
    }
    return root;
}

// Function to print each node data
// in level order
void printLevelATNewLine(TreeNode<int>* root)
{
    queue<TreeNode<int>*> q;
    q.push(root);
    q.push(NULL);
    while (!q.empty()) {

        TreeNode<int>* first = q.front();
        q.pop();

        if (first == NULL) {
            if (q.empty()) {
                break;
            }
            cout << endl;
            q.push(NULL);
            continue;
        }

        cout << first->data << " ";

        for (int i = 0;
             i < first->children.size(); i++) {
            q.push(first->children[i]);
        }
    }
}

// Helper function to replace the
// node data with their level value
void helper(TreeNode<int>* root,
            int depth)
{

    // Replace the node data with
    // it's depth
    root->data = depth;
    for (int i = 0;
         i < root->children.size(); i++) {

        helper(root->children[i], depth + 1);
    }
}

// Function to replace with depth
void replaceWithDepthValue(TreeNode<int>* root)
{
    helper(root, 0);
}

// Driver Code
int main()
{

    // Given level order traversal in
    // the array arr[]
    int arr[] = { 10, 3, 20, 30, 40, 2,
                  40, 50, 0, 0, 0, 0 };

    // Initialise Tree
    TreeNode<int>* root;
    root = takeInputLevelWise(arr);

    // Function call to replace with
    // depth value
    replaceWithDepthValue(root);

    // Function call to print
    // in level order
    printLevelATNewLine(root);
    return 0;
}

Java

// Java program to replace node with
// it's depth value

// Importing classes and interface
import java.util.ArrayList;
import java.util.LinkedList;
import java.util.Queue;

class GFG {
    // TreeNode class
    static class TreeNode<T> {
        // To store node value
        T data;

        // List of TreeNode to store
        // the child nodes
        ArrayList<TreeNode<T> > children;

        // Constructor to assign data to node
        TreeNode(T data)
        {
            this.data = data;
            children = new ArrayList<TreeNode<T> >();
        }
    }

    // Function to take input level wise
    // i.e., in level order traversal
    static TreeNode<Integer> takeInputLevelWise(int arr[])
    {
        int idx = 1;

        // Input root
        int rootData = arr[0];

        // Initialize tree with a root node
        TreeNode<Integer> root
            = new TreeNode<Integer>(rootData);

        // Initialize queue for appending
        // node as a child of parent in
        // N-ary tree
        Queue<TreeNode<Integer> > pendingNodes
            = new LinkedList<TreeNode<Integer> >();

        // Push the root node in queue
        pendingNodes.add(root);

        // While queue is not empty append
        // child to the node
        while (pendingNodes.size() != 0) {

            // Take the first node
            TreeNode<Integer> front = pendingNodes.peek();
            pendingNodes.poll();

            // Input number of its child
            int numChild = arr[idx];
            idx++;

            for (int i = 0; i < numChild; i++) {
                int childData = arr[idx];
                idx++;

                // Make child Node
                TreeNode<Integer> child
                    = new TreeNode<Integer>(childData);

                // Append child node to
                // it's parent
                front.children.add(child);
                pendingNodes.add(child);
            }
        }
        return root;
    }

    // Function to print each node data
    // in level order
    static void printLevelATNewLine(TreeNode<Integer> root)
    {
        Queue<TreeNode<Integer> > q
            = new LinkedList<TreeNode<Integer> >();
        q.add(root);
        q.add(null);
        while (!q.isEmpty()) {
            TreeNode<Integer> first = q.peek();
            q.poll();

            if (first == null) {
                // If there is no more nodes
                if (q.isEmpty()) {
                    break;
                }
                // All the nodes of current level are
                // visited
                System.out.println();
                q.add(null);
                continue;
            }

            System.out.print(first.data + " ");

            // Append current node's child to queue
            for (int i = 0; i < first.children.size();
                 i++) {
                q.add(first.children.get(i));
            }
        }
    }

    // Helper function to replace the
    // node data with their level value
    static void helper(TreeNode<Integer> root, int depth)
    {
        // Replace the node data with
        // it's depth
        root.data = depth;
        for (int i = 0; i < root.children.size(); i++) {
            helper(root.children.get(i), depth + 1);
        }
    }

    // Function to replace with depth
    static void
    replaceWithDepthValue(TreeNode<Integer> root)
    {
        helper(root, 0);
    }

    // Driver Code
    public static void main(String[] args)
    {
        // Given level order traversal in
        // the array arr[]
        int arr[]
            = { 10, 3, 20, 30, 40, 2, 40, 50, 0, 0, 0, 0 };

        // Initialise Tree
        TreeNode<Integer> root;
        root = takeInputLevelWise(arr);

        // Function call to replace with
        // depth value
        replaceWithDepthValue(root);

        // Function call to print
        // in level order
        printLevelATNewLine(root);
    }
}

// This code is contributed by jainlovely450

Output

0 
1 1 1 
2 2 

Time Complexity: O(N), where N is the number of nodes in Tree. 
Auxiliary Space: O(N), where N is the number of nodes in Tree.

Another Approach: We can also replace the node’s value with its depth while creating the tree. We are traversing the array level wise which means that nodes currently present in the queue are of the same depth. As we append its child nodes to the queue, they will be present in the next level. We can initialize a variable as current depth equal to 1 and when we create child node we can assign its value to current depth level. After traversing all the nodes present in the current level we will increment current depth level by 1.

C++

// C++ program to implement node with
// it's depth value
#include <bits/stdc++.h>
using namespace std;

// Treenode class using template
template <typename T> class TreeNode {
public:
    // To store node value
    T data;

    // Pointer to TreeNode to store
    // the child node
    vector<TreeNode<T>*> children;

    // Constructor to assign data
    // to node
    TreeNode(T data) { this->data = data; }

    // Destructors to delete a node
    ~TreeNode()
    {
        for (int i = 0; i < children.size(); i++) {
            delete children[i];
        }
    }
};

// Function to take input level wise
// i.e., in level order traversal
TreeNode<int>* takeInputLevelWise(int arr[])
{
    int idx = 1;
    int depthLevel = 1;

    // Initialize tree with a root node
    // with depth 0
    TreeNode<int>* root = new TreeNode<int>(0);

    // Initialise queue for appending
    // node as a child of parent in
    // N-ary tree
    queue<TreeNode<int>*> pendingNodes;

    // Push the root node in queue
    pendingNodes.push(root);

    // While queue is not empty append
    // child to the node
    while (pendingNodes.size() != 0) {
        // Number of nodes present in the current level
        int size = pendingNodes.size();

        while (size > 0) {
            // Take the first node
            TreeNode<int>* front = pendingNodes.front();
            pendingNodes.pop();

            // Input number of its child
            int numChild = arr[idx];
            idx++;

            for (int i = 0; i < numChild; i++) {
                idx++;
                // Make child Node and assign its data
                // value equal to depthLevel
                TreeNode<int>* child
                    = new TreeNode<int>(depthLevel);

                // Append child node to
                // it's parent
                front->children.push_back(child);
                pendingNodes.push(child);
            }
            size--;
        }
        // Increment depth level
        depthLevel++;
    }
    return root;
}

// Function to print each node data
// in level order
void printLevelATNewLine(TreeNode<int>* root)
{
    queue<TreeNode<int>*> q;
    q.push(root);
    q.push(NULL);
    while (!q.empty()) {
        TreeNode<int>* first = q.front();
        q.pop();

        if (first == NULL) {
            // If there is no more nodes to visit
            if (q.empty()) {
                break;
            }
            // All the nodes of current level are visited
            cout << endl;
            q.push(NULL);
            continue;
        }

        cout << first->data << " ";
        // Append current node's child to queue
        for (int i = 0; i < first->children.size(); i++) {
            q.push(first->children[i]);
        }
    }
}

// Driver Code
int main()
{
    // Given level order traversal in
    // the array arr[]
    int arr[]
        = { 10, 3, 20, 30, 40, 2, 40, 50, 0, 0, 0, 0 };

    // Initialise Tree
    TreeNode<int>* root;
    root = takeInputLevelWise(arr);

    // Function call to print
    // in level order
    printLevelATNewLine(root);
    return 0;
}

// This code is contributed by jainlovely450

Java

// Java program to implement node with
// it's depth value

// Importing classes and interface
import java.util.ArrayList;
import java.util.LinkedList;
import java.util.Queue;

public class GFG {

    // TreeNode class
    static class TreeNode<T> {
        // To store node value
        T data;

        // List of TreeNode to store
        // the child nodes
        ArrayList<TreeNode<T> > children;

        // Constructor to assign data to node
        TreeNode(T data)
        {
            this.data = data;
            children = new ArrayList<TreeNode<T> >();
        }
    }

    // Function to take input level wise
    // i.e., in level order traversal and
    // assign value of node equal to its depth
    static TreeNode<Integer> takeInputLevelWise(int arr[])
    {
        int idx = 1;
        int depthLevel = 1;

      // Initialize tree with a root node
        // with depth 0
        TreeNode<Integer> root = new TreeNode<Integer>(0);

        // Initialize queue for appending
        // node as a child of parent in
        // N-ary tree
        Queue<TreeNode<Integer> > pendingNodes
            = new LinkedList<TreeNode<Integer> >();

        // Push the root node in queue
        pendingNodes.add(root);

        // While queue is not empty append
        // child to the node
        while (!pendingNodes.isEmpty()) {
            // Number of nodes present in the current level
            int size = pendingNodes.size();

            while (size > 0) {
                TreeNode<Integer> front
                    = pendingNodes.peek();
                pendingNodes.poll();

                // Input number of child
                int numChild = arr[idx];
                idx++;
                for (int i = 0; i < numChild; i++) {
                    idx++;

                    // Make child Node and assign its data
                    // value equal to depthLevel
                    TreeNode<Integer> child
                        = new TreeNode<Integer>(depthLevel);

                    // Append child node to
                    // it's parent
                    front.children.add(child);
                    pendingNodes.add(child);
                }
                size--;
            }
            // Increment depth level
            depthLevel++;
        }
        return root;
    }

    // Function to print each node data
    // in level order
    static void printLevelATNewLine(TreeNode<Integer> root)
    {
        Queue<TreeNode<Integer> > q
            = new LinkedList<TreeNode<Integer> >();
        q.add(root);
        q.add(null);
        while (!q.isEmpty()) {
            TreeNode<Integer> first = q.peek();
            q.poll();
            if (first == null) {
                // If there is no more nodes to visit
                if (q.isEmpty()) {
                    break;
                }
                // All the nodes of current level are
                // visited
                System.out.println();
                q.add(null);
                continue;
            }

            System.out.print(first.data + " ");

            // Append current node's child to queue
            for (int i = 0; i < first.children.size();
                 i++) {
                q.add(first.children.get(i));
            }
        }
    }

    // Driver Code
    public static void main(String[] args)
    {

        // Given level order traversal in
        // the array arr[]
        int arr[]
            = { 10, 3, 20, 30, 40, 2, 40, 50, 0, 0, 0, 0 };

        // Initialize Tree
        TreeNode<Integer> root;
        root = takeInputLevelWise(arr);

        // Function call to print
        // in level order
        printLevelATNewLine(root);
    }
}

// This code is contributed by jainlovely450

Output

0 
1 1 1 
2 2