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Creating a tree with Left-Child Right-Sibling Representation
• Difficulty Level : Medium
• Last Updated : 29 Dec, 2020

Left-Child Right-Sibling Representation is a different representation of an n-ary tree where instead of holding a reference to each and every child node, a node holds just two references, first a reference to it’s first child, and the other to it’s immediate next sibling. This new transformation not only removes the need of advance knowledge of the number of children a node has, but also limits the number of references to a maximum of two, thereby making it so much easier to code.

```At each node, link children of same parent from left to right.
Parent should be linked with only first child.```

Examples:

```Left Child Right Sibling tree representation
10
|
2 -> 3 -> 4 -> 5
|    |
6    7 -> 8 -> 9```

Prerequisite : Left-Child Right-Sibling Representation of Tree

Below is the implementation.

## C++

 `// C++ program to create a tree with left child` `// right sibling representation.` `#include` `using` `namespace` `std;`   `struct` `Node` `{` `    ``int` `data;` `    ``struct` `Node *next;` `    ``struct` `Node *child;` `};`   `// Creating new Node` `Node* newNode(``int` `data)` `{` `    ``Node *newNode = ``new` `Node;` `    ``newNode->next = newNode->child = NULL;` `    ``newNode->data = data;` `    ``return` `newNode;` `}`   `// Adds a sibling to a list with starting with n` `Node *addSibling(Node *n, ``int` `data)` `{` `    ``if` `(n == NULL)` `        ``return` `NULL;`   `    ``while` `(n->next)` `        ``n = n->next;`   `    ``return` `(n->next = newNode(data));` `}`   `// Add child Node to a Node` `Node *addChild(Node * n, ``int` `data)` `{` `    ``if` `(n == NULL)` `        ``return` `NULL;`   `    ``// Check if child list is not empty.` `    ``if` `(n->child)` `        ``return` `addSibling(n->child, data);` `    ``else` `        ``return` `(n->child = newNode(data));` `}`   `// Traverses tree in depth first order` `void` `traverseTree(Node * root)` `{` `    ``if` `(root == NULL)` `        ``return``;`   `    ``while` `(root)` `    ``{` `        ``cout << ``" "` `<< root->data;` `        ``if` `(root->child)` `            ``traverseTree(root->child);` `        ``root = root->next;` `    ``}` `}`   `//Driver code`   `int` `main()` `{` `    ``/*   Let us create below tree` `    ``*           10` `    ``*     /   /    \   \` `    ``*    2  3      4   5` `    ``*              |   /  | \` `    ``*              6   7  8  9   */`   `    ``// Left child right sibling` `    ``/*  10` `    ``*    |` `    ``*    2 -> 3 -> 4 -> 5` `    ``*              |    |` `    ``*              6    7 -> 8 -> 9  */` `    ``Node *root = newNode(10);` `    ``Node *n1  = addChild(root, 2);` `    ``Node *n2  = addChild(root, 3);` `    ``Node *n3  = addChild(root, 4);` `    ``Node *n4  = addChild(n3, 6);` `    ``Node *n5  = addChild(root, 5);` `    ``Node *n6  = addChild(n5, 7);` `    ``Node *n7  = addChild(n5, 8);` `    ``Node *n8  = addChild(n5, 9);` `    ``traverseTree(root);` `    ``return` `0;` `}`

## Java

 `// Java program to create a tree with left child` `// right sibling representation. `   `class` `GFG {` `    `  `    ``static` `class` `NodeTemp` `    ``{` `        ``int` `data;` `        ``NodeTemp next, child;` `        ``public` `NodeTemp(``int` `data)` `        ``{` `            ``this``.data = data;` `            ``next = child = ``null``;` `        ``}` `    ``}` `    `  `    ``// Adds a sibling to a list with starting with n` `    ``static` `public` `NodeTemp addSibling(NodeTemp node, ``int` `data)` `    ``{` `        ``if``(node == ``null``)` `            ``return` `null``;` `        ``while``(node.next != ``null``)` `            ``node = node.next;` `        ``return``(node.next = ``new` `NodeTemp(data));` `    ``}` `        `  `    ``// Add child Node to a Node` `    ``static` `public` `NodeTemp addChild(NodeTemp node,``int` `data)` `    ``{` `        ``if``(node == ``null``)` `            ``return` `null``;` `    `  `        ``// Check if child is not empty.` `        ``if``(node.child != ``null``)` `            ``return``(addSibling(node.child,data));` `        ``else` `            ``return``(node.child = ``new` `NodeTemp(data));` `    ``}`   `    ``// Traverses tree in depth first order` `    ``static` `public` `void` `traverseTree(NodeTemp root)` `    ``{` `        ``if``(root == ``null``)` `            ``return``;` `        ``while``(root != ``null``)` `        ``{` `            ``System.out.print(root.data + ``" "``);` `            ``if``(root.child != ``null``)` `                ``traverseTree(root.child);` `            ``root = root.next;` `        ``}` `    ``}`   `    ``// Driver code` `    ``public` `static` `void` `main(String args[])` `    ``{` `        `  `        ``/*   Let us create below tree` `        ``*           10` `        ``*     /   /    \   \` `        ``*    2  3      4   5` `        ``*              |   /  | \` `        ``*              6   7  8  9   */` `     `  `        ``// Left child right sibling` `        ``/*  10` `        ``*    |` `        ``*    2 -> 3 -> 4 -> 5` `        ``*              |    |` `        ``*              6    7 -> 8 -> 9  */`   `        ``NodeTemp root = ``new` `NodeTemp(``10``);` `        ``NodeTemp n1 = addChild(root,``2``);` `        ``NodeTemp n2 = addChild(root,``3``);` `        ``NodeTemp n3 = addChild(root,``4``);` `        ``NodeTemp n4 = addChild(n3,``6``);` `        ``NodeTemp n5 = addChild(root,``5``);` `        ``NodeTemp n6 = addChild(n5,``7``);` `        ``NodeTemp n7 = addChild(n5,``8``);` `        ``NodeTemp n8 = addChild(n5,``9``);` `        `  `        ``traverseTree(root);` `    ``}` `}`   `// This code is contributed by M.V.S.Surya Teja.`

## Python3

 `# Python3 program to create a tree with ` `# left child right sibling representation. `   `# Creating new Node ` `class` `newNode:` `    ``def` `__init__(``self``, data):` `        ``self``.``Next` `=` `self``.child ``=` `None` `        ``self``.data ``=` `data`   `# Adds a sibling to a list with` `# starting with n ` `def` `addSibling(n, data):` `    ``if` `(n ``=``=` `None``):` `        ``return` `None`   `    ``while` `(n.``Next``):` `        ``n ``=` `n.``Next` `    ``n.``Next` `=` `newNode(data)` `    ``return` `n.``Next`   `# Add child Node to a Node ` `def` `addChild(n, data):` `    ``if` `(n ``=``=` `None``):` `        ``return` `None`   `    ``# Check if child list is not empty. ` `    ``if` `(n.child): ` `        ``return` `addSibling(n.child, data) ` `    ``else``:` `        ``n.child ``=` `newNode(data)` `        ``return` `n.child`   `# Traverses tree in depth first order ` `def` `traverseTree(root):` `    ``if` `(root ``=``=` `None``):` `        ``return`   `    ``while` `(root):` `        ``print``(root.data, end ``=` `" "``) ` `        ``if` `(root.child):` `            ``traverseTree(root.child) ` `        ``root ``=` `root.``Next`   `# Driver code ` `if` `__name__ ``=``=` `'__main__'``:` `    `  `    ``# Let us create below tree ` `    ``#         10 ` `    ``#     / / \ \ ` `    ``# 2 3     4 5 ` `    ``#             | / | \ ` `    ``#             6 7 8 9 `   `    ``# Left child right sibling ` `    ``# 10 ` `    ``# | ` `    ``# 2 -> 3 -> 4 -> 5 ` `    ``#             | | ` `    ``#             6 7 -> 8 -> 9 ` `    ``root ``=` `newNode(``10``) ` `    ``n1 ``=` `addChild(root, ``2``) ` `    ``n2 ``=` `addChild(root, ``3``) ` `    ``n3 ``=` `addChild(root, ``4``) ` `    ``n4 ``=` `addChild(n3, ``6``) ` `    ``n5 ``=` `addChild(root, ``5``) ` `    ``n6 ``=` `addChild(n5, ``7``) ` `    ``n7 ``=` `addChild(n5, ``8``) ` `    ``n8 ``=` `addChild(n5, ``9``) ` `    ``traverseTree(root)` `    `  `# This code is contributed by pranchalK`

## C#

 `// C# program to create a tree with left ` `// child right sibling representation. ` `using` `System;`   `class` `GFG` `{` `public` `class` `NodeTemp` `{` `    ``public` `int` `data;` `    ``public` `NodeTemp next, child;` `    ``public` `NodeTemp(``int` `data)` `    ``{` `        ``this``.data = data;` `        ``next = child = ``null``;` `    ``}` `}`   `// Adds a sibling to a list with` `// starting with n ` `public` `static` `NodeTemp addSibling(NodeTemp node,` `                                  ``int` `data)` `{` `    ``if` `(node == ``null``)` `    ``{` `        ``return` `null``;` `    ``}` `    ``while` `(node.next != ``null``)` `    ``{` `        ``node = node.next;` `    ``}` `    ``return` `(node.next = ``new` `NodeTemp(data));` `}`   `// Add child Node to a Node ` `public` `static` `NodeTemp addChild(NodeTemp node,` `                                ``int` `data)` `{` `    ``if` `(node == ``null``)` `    ``{` `        ``return` `null``;` `    ``}`   `    ``// Check if child is not empty. ` `    ``if` `(node.child != ``null``)` `    ``{` `        ``return` `(addSibling(node.child,data));` `    ``}` `    ``else` `    ``{` `        ``return` `(node.child = ``new` `NodeTemp(data));` `    ``}` `}`   `// Traverses tree in depth first order ` `public` `static` `void` `traverseTree(NodeTemp root)` `{` `    ``if` `(root == ``null``)` `    ``{` `        ``return``;` `    ``}` `    ``while` `(root != ``null``)` `    ``{` `        ``Console.Write(root.data + ``" "``);` `        ``if` `(root.child != ``null``)` `        ``{` `            ``traverseTree(root.child);` `        ``}` `        ``root = root.next;` `    ``}` `}`   `// Driver code ` `public` `static` `void` `Main(``string``[] args)` `{`   `    ``/* Let us create below tree ` `    ``*         10 ` `    ``*     / / \ \ ` `    ``* 2 3     4 5 ` `    ``*             | / | \ ` `    ``*             6 7 8 9 */`   `    ``// Left child right sibling ` `    ``/* 10 ` `    ``* | ` `    ``* 2 -> 3 -> 4 -> 5 ` `    ``*             | | ` `    ``*             6 7 -> 8 -> 9 */`   `    ``NodeTemp root = ``new` `NodeTemp(10);` `    ``NodeTemp n1 = addChild(root, 2);` `    ``NodeTemp n2 = addChild(root, 3);` `    ``NodeTemp n3 = addChild(root, 4);` `    ``NodeTemp n4 = addChild(n3, 6);` `    ``NodeTemp n5 = addChild(root, 5);` `    ``NodeTemp n6 = addChild(n5, 7);` `    ``NodeTemp n7 = addChild(n5, 8);` `    ``NodeTemp n8 = addChild(n5, 9);`   `    ``traverseTree(root);` `}` `}`   `// This code is contributed by Shrikant13`

Output:

`10 2 3 4 6 5 7 8 9`

Level Order Traversal : The above code talks about depth first traversal. We can also do level order traversal of such representation.

## C++

 `// C++ program to create a tree with left child` `// right sibling representation.` `#include ` `using` `namespace` `std;`   `struct` `Node {` `    ``int` `data;` `    ``struct` `Node* next;` `    ``struct` `Node* child;` `};`   `// Creating new Node` `Node* newNode(``int` `data)` `{` `    ``Node* newNode = ``new` `Node;` `    ``newNode->next = newNode->child = NULL;` `    ``newNode->data = data;` `    ``return` `newNode;` `}`   `// Adds a sibling to a list with starting with n` `Node* addSibling(Node* n, ``int` `data)` `{` `    ``if` `(n == NULL)` `        ``return` `NULL;`   `    ``while` `(n->next)` `        ``n = n->next;`   `    ``return` `(n->next = newNode(data));` `}`   `// Add child Node to a Node` `Node* addChild(Node* n, ``int` `data)` `{` `    ``if` `(n == NULL)` `        ``return` `NULL;`   `    ``// Check if child list is not empty.` `    ``if` `(n->child)` `        ``return` `addSibling(n->child, data);` `    ``else` `        ``return` `(n->child = newNode(data));` `}`   `// Traverses tree in level order` `void` `traverseTree(Node* root)` `{` `    ``// Corner cases` `    ``if` `(root == NULL)` `        ``return``;`   `    ``cout << root->data << ``" "``;`   `    ``if` `(root->child == NULL)` `        ``return``;`   `    ``// Create a queue and enque root` `    ``queue q;` `    ``Node* curr = root->child;` `    ``q.push(curr);`   `    ``while` `(!q.empty()) {`   `        ``// Take out an item from the queue` `        ``curr = q.front();` `        ``q.pop();`   `        ``// Print next level of taken out item and enque` `        ``// next level's children ` `        ``while` `(curr != NULL) {` `            ``cout << curr->data << ``" "``;` `            ``if` `(curr->child != NULL) {` `                ``q.push(curr->child);` `            ``}` `            ``curr = curr->next;` `        ``}` `    ``}` `}`   `// Driver code` `int` `main()` `{` `    ``Node* root = newNode(10);` `    ``Node* n1 = addChild(root, 2);` `    ``Node* n2 = addChild(root, 3);` `    ``Node* n3 = addChild(root, 4);` `    ``Node* n4 = addChild(n3, 6);` `    ``Node* n5 = addChild(root, 5);` `    ``Node* n6 = addChild(n5, 7);` `    ``Node* n7 = addChild(n5, 8);` `    ``Node* n8 = addChild(n5, 9);` `    ``traverseTree(root);` `    ``return` `0;` `}`

## Python3

 `# Python3 program to create a tree with` `# left child right sibling representation` `from` `collections ``import` `deque`   `class` `Node:` `    `  `    ``def` `__init__(``self``, x):` `        `  `        ``self``.data ``=` `x` `        ``self``.``next` `=` `None` `        ``self``.child ``=` `None`   `# Adds a sibling to a list with ` `# starting with n` `def` `addSibling(n, data):` `    `  `    ``if` `(n ``=``=` `None``):` `        ``return` `None`   `    ``while` `(n.``next``):` `        ``n ``=` `n.``next`   `    ``n.``next` `=` `Node(data)` `    ``return` `n`   `# Add child Node to a Node` `def` `addChild(n, data):` `    `  `    ``if` `(n ``=``=` `None``):` `        ``return` `None` `        `  `    ``# Check if child list is not empty` `    ``if` `(n.child):` `        ``return` `addSibling(n.child, data)` `    ``else``:` `        ``n.child ``=` `Node(data)` `        ``return` `n`   `# Traverses tree in level order` `def` `traverseTree(root):` `    `  `    ``# Corner cases` `    ``if` `(root ``=``=` `None``):` `        ``return`   `    ``print``(root.data, end ``=` `" "``)`   `    ``if` `(root.child ``=``=` `None``):` `        ``return`   `    ``# Create a queue and enque root` `    ``q ``=` `deque()` `    ``curr ``=` `root.child` `    ``q.append(curr)`   `    ``while` `(``len``(q) > ``0``):` `        `  `        ``# Take out an item from the queue` `        ``curr ``=` `q.popleft()` `        ``#q.pop()`   `        ``# Print next level of taken out ` `        ``# item and enque next level's children` `        ``while` `(curr !``=` `None``):` `            ``print``(curr.data, end ``=` `" "``)` `            `  `            ``if` `(curr.child !``=` `None``):` `                ``q.append(curr.child)` `                `  `            ``curr ``=` `curr.``next`   `# Driver code` `if` `__name__ ``=``=` `'__main__'``:`   `    ``root ``=` `Node(``10``)` `    ``n1 ``=` `addChild(root, ``2``)` `    ``n2 ``=` `addChild(root, ``3``)` `    ``n3 ``=` `addChild(root, ``4``)` `    ``n4 ``=` `addChild(n3, ``6``)` `    ``n5 ``=` `addChild(root, ``5``)` `    ``n6 ``=` `addChild(n5, ``7``)` `    ``n7 ``=` `addChild(n5, ``8``)` `    ``n8 ``=` `addChild(n5, ``9``)` `    `  `    ``traverseTree(root)`   `# This code is contributed by mohit kumar 29`

Output:

`10 2 3 4 5 6 7 8 9`

This article is contributed by SAKSHI TIWARI. If you like GeeksforGeeks(We know you do!) and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.
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