# Print nodes at k distance from root | Iterative

Given a root of a tree, and an integer k. Print all the nodes which are at k distance from root.

Example :

```Input :
20
/   \
10    30
/ \    / \
5  15  25  40
/
12

and k = 3
Root is at level 1.

Output :
5 15 25 40
```

## Recommended: Please solve it on “PRACTICE” first, before moving on to the solution.

Recursive approach to this problem is discussed here
Following is the iterative approach.
The solution is similar to Getting level of node in Binary Tree

## C++

 `// CPP program to print all nodes of level k ` `// iterative approach  ` `/* binary tree ` `root is at level 1 ` ` `  `                ``20 ` `              ``/   \ ` `            ``10    30 ` `           ``/ \    / \ ` `          ``5  15  25  40 ` `             ``/ ` `            ``12  */` `#include ` `using` `namespace` `std; ` ` `  `// Node of binary tree ` `struct` `Node { ` `    ``int` `data; ` `    ``Node* left, * right; ` `}; ` ` `  `// Function to add a new node ` `Node* newNode(``int` `data) ` `{ ` `    ``Node* newnode = ``new` `Node(); ` `    ``newnode->data = data; ` `    ``newnode->left = newnode->right = NULL; ` `} ` ` `  `// Function to print nodes of given level ` `bool` `printKDistant(Node* root, ``int` `klevel) ` `{ ` `    ``queue q; ` `    ``int` `level = 1; ` `    ``bool` `flag = ``false``; ` `    ``q.push(root); ` ` `  `    ``// extra NULL is pushed to keep track ` `    ``// of all the nodes to be pushed before ` `    ``// level is incremented by 1 ` `    ``q.push(NULL); ` `    ``while` `(!q.empty()) { ` `        ``Node* temp = q.front(); ` ` `  `        ``// print when level is equal to k ` `        ``if` `(level == klevel && temp != NULL) { ` `            ``flag = ``true``; ` `            ``cout << temp->data << ``" "``; ` `        ``} ` `        ``q.pop(); ` `        ``if` `(temp == NULL) { ` `            ``if` `(q.front()) ` `                ``q.push(NULL); ` `            ``level += 1; ` ` `  `            ``// break the loop if level exceeds ` `            ``// the given level number ` `            ``if` `(level > klevel) ` `                ``break``; ` `        ``} ``else` `{ ` `            ``if` `(temp->left) ` `                ``q.push(temp->left); ` ` `  `            ``if` `(temp->right) ` `                ``q.push(temp->right); ` `        ``} ` `    ``} ` `    ``cout << endl; ` ` `  `    ``return` `flag; ` `} ` ` `  `// Driver code ` `int` `main() ` `{ ` `    ``// create a binary tree ` `    ``Node* root = newNode(20); ` `    ``root->left = newNode(10); ` `    ``root->right = newNode(30); ` `    ``root->left->left = newNode(5); ` `    ``root->left->right = newNode(15); ` `    ``root->left->right->left = newNode(12); ` `    ``root->right->left = newNode(25); ` `    ``root->right->right = newNode(40); ` ` `  `    ``cout << ``"data at level 1 : "``; ` `    ``int` `ret = printKDistant(root, 1); ` `    ``if` `(ret == ``false``) ` `        ``cout << ``"Number exceeds total number of levels\n"``; ` ` `  `    ``cout << ``"data at level 2 : "``; ` `    ``ret = printKDistant(root, 2); ` `    ``if` `(ret == ``false``) ` `        ``cout << ``"Number exceeds total number of levels\n"``; ` ` `  `    ``cout << ``"data at level 3 : "``; ` `    ``ret = printKDistant(root, 3); ` `    ``if` `(ret == ``false``) ` `        ``cout << ``"Number exceeds total number of levels\n"``; ` ` `  `    ``cout << ``"data at level 6 : "``; ` `    ``ret = printKDistant(root, 6); ` `    ``if` `(ret == ``false``) ` `        ``cout << ``"Number exceeds total number of levels\n"``; ` ` `  `    ``return` `0; ` `} `

## Java

 `// Java program to print all nodes of level k  ` `// iterative approach  ` `/* binary tree  ` `root is at level 1  ` ` `  `                ``20  ` `            ``/ \  ` `            ``10 30  ` `        ``/ \ / \  ` `        ``5 15 25 40  ` `            ``/  ` `            ``12 */` `             `  `import` `java.util.*; ` `class` `GFG ` `{ ` ` `  `// Node of binary tree  ` `static` `class` `Node  ` `{  ` `    ``int` `data;  ` `    ``Node left, right;  ` `} ` ` `  `// Function to add a new node  ` `static` `Node newNode(``int` `data)  ` `{  ` `    ``Node newnode = ``new` `Node();  ` `    ``newnode.data = data;  ` `    ``newnode.left = newnode.right = ``null``;  ` `    ``return` `newnode; ` `}  ` ` `  `// Function to print nodes of given level  ` `static` `boolean` `printKDistant(Node root, ``int` `klevel)  ` `{  ` `    ``Queue q = ``new` `LinkedList<>();  ` `    ``int` `level = ``1``;  ` `    ``boolean` `flag = ``false``;  ` `    ``q.add(root);  ` ` `  `    ``// extra null is added to keep track  ` `    ``// of all the nodes to be added before  ` `    ``// level is incremented by 1  ` `    ``q.add(``null``);  ` `    ``while` `(q.size() > ``0``)  ` `    ``{  ` `        ``Node temp = q.peek();  ` ` `  `        ``// print when level is equal to k  ` `        ``if` `(level == klevel && temp != ``null``) ` `        ``{  ` `            ``flag = ``true``;  ` `            ``System.out.print( temp.data + ``" "``);  ` `        ``}  ` `        ``q.remove();  ` `        ``if` `(temp == ``null``) ` `        ``{  ` `            ``if` `(q.peek() != ``null``)  ` `                ``q.add(``null``);  ` `            ``level += ``1``;  ` ` `  `            ``// break the loop if level exceeds  ` `            ``// the given level number  ` `            ``if` `(level > klevel)  ` `                ``break``;  ` `        ``} ` `        ``else`  `        ``{  ` `            ``if` `(temp.left != ``null``)  ` `                ``q.add(temp.left);  ` ` `  `            ``if` `(temp.right != ``null``)  ` `                ``q.add(temp.right);  ` `        ``}  ` `    ``}  ` `    ``System.out.println(); ` `    ``return` `flag;  ` `}  ` ` `  `// Driver code  ` `public` `static` `void` `main(String srga[]) ` `{  ` `    ``// create a binary tree  ` `    ``Node root = newNode(``20``);  ` `    ``root.left = newNode(``10``);  ` `    ``root.right = newNode(``30``);  ` `    ``root.left.left = newNode(``5``);  ` `    ``root.left.right = newNode(``15``);  ` `    ``root.left.right.left = newNode(``12``);  ` `    ``root.right.left = newNode(``25``);  ` `    ``root.right.right = newNode(``40``);  ` ` `  `    ``System.out.print( ``"data at level 1 : "``);  ` `    ``boolean` `ret = printKDistant(root, ``1``);  ` `    ``if` `(ret == ``false``)  ` `        ``System.out.print( ``"Number exceeds total "` `+  ` `                            ``"number of levels\n"``);  ` ` `  `    ``System.out.print(``"data at level 2 : "``);  ` `    ``ret = printKDistant(root, ``2``);  ` `    ``if` `(ret == ``false``)  ` `        ``System.out.print(``"Number exceeds total "` `+ ` `                            ``"number of levels\n"``);  ` ` `  `    ``System.out.print( ``"data at level 3 : "``);  ` `    ``ret = printKDistant(root, ``3``);  ` `    ``if` `(ret == ``false``)  ` `        ``System.out.print(``"Number exceeds total "` `+ ` `                        ``"number of levels\n"``);  ` ` `  `    ``System.out.print( ``"data at level 6 : "``);  ` `    ``ret = printKDistant(root, ``6``);  ` `    ``if` `(ret == ``false``)  ` `        ``System.out.print( ``"Number exceeds total"` `+ ` `                            ``"number of levels\n"``);  ` ` `  `}  ` `} ` ` `  `// This code is contributed by Arnab Kundu `

## Python3

 `# Python3 program to print all nodes of level k  ` `# iterative approach  ` `""" binary tree  ` `root is at level 1  ` ` `  `                ``20  ` `            ``/ \  ` `            ``10 30  ` `        ``/ \ / \  ` `        ``5 15 25 40  ` `            ``/  ` `            ``12 """` ` `  `# Node of binary tree  ` `# Function to add a new node ` `class` `newNode:  ` `    ``def` `__init__(``self``, data):  ` `        ``self``.data ``=` `data  ` `        ``self``.left ``=` `self``.right ``=` `None` `         `  `# Function to prnodes of given level  ` `def` `printKDistant( root, klevel): ` ` `  `    ``q ``=` `[]  ` `    ``level ``=` `1` `    ``flag ``=` `False` `    ``q.append(root)  ` ` `  `    ``# extra None is appended to keep track  ` `    ``# of all the nodes to be appended  ` `    ``# before level is incremented by 1  ` `    ``q.append(``None``)  ` `    ``while` `(``len``(q)): ` `        ``temp ``=` `q[``0``]  ` ` `  `        ``# prwhen level is equal to k  ` `        ``if` `(level ``=``=` `klevel ``and` `temp !``=` `None``): ` `            ``flag ``=` `True` `            ``print``(temp.data, end ``=` `" "``) ` `         `  `        ``q.pop(``0``)  ` `        ``if` `(temp ``=``=` `None``) : ` `            ``if` `(``len``(q)):  ` `                ``q.append(``None``)  ` `            ``level ``+``=` `1` ` `  `            ``# break the loop if level exceeds  ` `            ``# the given level number  ` `            ``if` `(level > klevel) : ` `                ``break` `        ``else``: ` `            ``if` `(temp.left) : ` `                ``q.append(temp.left)  ` ` `  `            ``if` `(temp.right) : ` `                ``q.append(temp.right)  ` `    ``print``() ` ` `  `    ``return` `flag ` `     `  `# Driver Code  ` `if` `__name__ ``=``=` `'__main__'``: ` `    ``root ``=` `newNode(``20``)  ` `    ``root.left ``=` `newNode(``10``)  ` `    ``root.right ``=` `newNode(``30``)  ` `    ``root.left.left ``=` `newNode(``5``)  ` `    ``root.left.right ``=` `newNode(``15``)  ` `    ``root.left.right.left ``=` `newNode(``12``)  ` `    ``root.right.left ``=` `newNode(``25``)  ` `    ``root.right.right ``=` `newNode(``40``)  ` ` `  `    ``print``(``"data at level 1 : "``, end ``=` `"") ` `    ``ret ``=` `printKDistant(root, ``1``)  ` `    ``if` `(ret ``=``=` `False``):  ` `        ``print``(``"Number exceeds total"``, ` `                  ``"number of levels"``) ` ` `  `    ``print``(``"data at level 2 : "``, end ``=` `"") ` `    ``ret ``=` `printKDistant(root, ``2``)  ` `    ``if` `(ret ``=``=` `False``) : ` `        ``print``(``"Number exceeds total"``,  ` `                  ``"number of levels"``)  ` ` `  `    ``print``(``"data at level 3 : "``, end ``=` `"") ` `    ``ret ``=` `printKDistant(root, ``3``)  ` `    ``if` `(ret ``=``=` `False``) : ` `        ``print``(``"Number exceeds total"``, ` `                  ``"number of levels"``) ` ` `  `    ``print``(``"data at level 6 : "``, end ``=` `"")  ` `    ``ret ``=` `printKDistant(root, ``6``)  ` `    ``if` `(ret ``=``=` `False``): ` `        ``print``(``"Number exceeds total number of levels"``) ` ` `  `# This code is contributed  ` `# by SHUBHAMSINGH10 `

## C#

 `// C# program to print all nodes of level k  ` `// iterative approach  ` `/* binary tree  ` `root is at level 1  ` ` `  `                ``20  ` `            ``/ \  ` `            ``10 30  ` `        ``/ \ / \  ` `        ``5 15 25 40  ` `            ``/  ` `            ``12 */` `             `  `using` `System; ` `using` `System.Collections.Generic; ` ` `  `class` `GFG  ` `{  ` ` `  `// Node of binary tree  ` `public` `class` `Node  ` `{  ` `    ``public` `int` `data;  ` `    ``public` `Node left, right;  ` `}  ` ` `  `// Function to add a new node  ` `static` `Node newNode(``int` `data)  ` `{  ` `    ``Node newnode = ``new` `Node();  ` `    ``newnode.data = data;  ` `    ``newnode.left = newnode.right = ``null``;  ` `    ``return` `newnode;  ` `}  ` ` `  `// Function to print nodes of given level  ` `static` `Boolean printKDistant(Node root, ``int` `klevel)  ` `{  ` `    ``Queue q = ``new` `Queue();  ` `    ``int` `level = 1;  ` `    ``Boolean flag = ``false``;  ` `    ``q.Enqueue(root);  ` ` `  `    ``// extra null is added to keep track  ` `    ``// of all the nodes to be added before  ` `    ``// level is incremented by 1  ` `    ``q.Enqueue(``null``);  ` `    ``while` `(q.Count > 0)  ` `    ``{  ` `        ``Node temp = q.Peek();  ` ` `  `        ``// print when level is equal to k  ` `        ``if` `(level == klevel && temp != ``null``)  ` `        ``{  ` `            ``flag = ``true``;  ` `            ``Console.Write( temp.data + ``" "``);  ` `        ``}  ` `        ``q.Dequeue();  ` `        ``if` `(temp == ``null``)  ` `        ``{  ` `            ``if` `(q.Count > 0&&q.Peek() != ``null``)  ` `                ``q.Enqueue(``null``);  ` `            ``level += 1;  ` ` `  `            ``// break the loop if level exceeds  ` `            ``// the given level number  ` `            ``if` `(level > klevel)  ` `                ``break``;  ` `        ``}  ` `        ``else` `        ``{  ` `            ``if` `(temp.left != ``null``)  ` `                ``q.Enqueue(temp.left);  ` ` `  `            ``if` `(temp.right != ``null``)  ` `                ``q.Enqueue(temp.right);  ` `        ``}  ` `    ``}  ` `    ``Console.Write(``"\n"``);  ` `    ``return` `flag;  ` `}  ` ` `  `// Driver code  ` `public` `static` `void` `Main(String []srga)  ` `{  ` `    ``// create a binary tree  ` `    ``Node root = newNode(20);  ` `    ``root.left = newNode(10);  ` `    ``root.right = newNode(30);  ` `    ``root.left.left = newNode(5);  ` `    ``root.left.right = newNode(15);  ` `    ``root.left.right.left = newNode(12);  ` `    ``root.right.left = newNode(25);  ` `    ``root.right.right = newNode(40);  ` ` `  `    ``Console.Write( ``"data at level 1 : "``);  ` `    ``Boolean ret = printKDistant(root, 1);  ` `    ``if` `(ret == ``false``)  ` `        ``Console.Write( ``"Number exceeds total "` `+  ` `                            ``"number of levels\n"``);  ` ` `  `    ``Console.Write(``"data at level 2 : "``);  ` `    ``ret = printKDistant(root, 2);  ` `    ``if` `(ret == ``false``)  ` `        ``Console.Write(``"Number exceeds total "` `+  ` `                            ``"number of levels\n"``);  ` ` `  `    ``Console.Write( ``"data at level 3 : "``);  ` `    ``ret = printKDistant(root, 3);  ` `    ``if` `(ret == ``false``)  ` `        ``Console.Write(``"Number exceeds total "` `+  ` `                        ``"number of levels\n"``);  ` ` `  `    ``Console.Write( ``"data at level 6 : "``);  ` `    ``ret = printKDistant(root, 6);  ` `    ``if` `(ret == ``false``)  ` `        ``Console.Write( ``"Number exceeds total"` `+  ` `                            ``"number of levels\n"``);  ` ` `  `}  ` `}  ` ` `  `// This code is contributed by Princi Singh `

Output:

```data at level 1 : 20
data at level 2 : 10 30
data at level 3 : 5 15 25 40
data at level 6 :
Number exceeds total number of levels
```

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