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Replace every node with depth in N-ary Generic Tree
• Difficulty Level : Medium
• Last Updated : 11 Jun, 2021

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 ` `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*> 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;`   `    ``// Initialize tree with a root node` `    ``TreeNode<``int``>* root` `        ``= ``new` `TreeNode<``int``>(rootData);`   `    ``// Intialise queue for appending` `    ``// node as a child of parent in` `    ``// N-ary tree` `    ``queue*> 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*> 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 };`   `    ``// Intialise 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;` `}`

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.

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