Open In App

Print path from root to all nodes in a Complete Binary Tree

Given a number N which is the total number of nodes in a complete binary tree where nodes are number from 1 to N sequentially level-wise. The task is to write a program to print paths from root to all of the nodes in the Complete Binary Tree.
For N = 3, the tree will be:

```     1
/     \
2        3 ```

For N = 7, the tree will be:

```       1
/     \
2        3
/   \    /  \
4    5    6   7```

Examples:

```Input : 7
Output :
1
1 2
1 2 4
1 2 5
1 3
1 3 6
1 3 7

Input : 4
Output :
1
1 2
1 2 4
1 3 ```

Explanation:- Since, the given tree is a complete binary tree. For every node we can calculate its left child as 2*i and right child as 2*i + 1.
The idea is to use a backtracking approach to print all paths. Maintain a vector to store paths, initially push the root node 1 to it, and before pushing the left and right children print the current path stored in it and then call the function for the left and right children as well.
Below is the complete implementation of the above approach:

C++

 `// C++ program to print path from root to all``// nodes in a complete binary tree.` `#include ``#include ``using` `namespace` `std;` `// Function to print path of all the nodes``// nth node represent as given node``// kth node represents as left and right node``void` `printPath(vector<``int``> res, ``int` `nThNode, ``int` `kThNode)``{``    ``// base condition``    ``// if kth node value is greater``    ``// then nth node then its means``    ``// kth node is not valid so``    ``// we not store it into the res``    ``// simply we just return``    ``if` `(kThNode > nThNode)``        ``return``;` `    ``// Storing node into res``    ``res.push_back(kThNode);` `    ``// Print the path from root to node``    ``for` `(``int` `i = 0; i < res.size(); i++)``        ``cout << res[i] << ``" "``;``    ``cout << ``"\n"``;` `    ``// store left path of a tree``    ``// So for left we will go node(kThNode*2)``    ``printPath(res, nThNode, kThNode * 2);` `    ``// right path of a tree``    ``// and for right we will go node(kThNode*2+1)``    ``printPath(res, nThNode, kThNode * 2 + 1);``}` `// Function to print path from root to all of the nodes``void` `printPathToCoverAllNodeUtil(``int` `nThNode)``{``    ``// res is for store the path``    ``// from root to particulate node``    ``vector<``int``> res;` `    ``// Print path from root to all node.``    ``// third argument 1 because of we have``    ``// to consider root node is 1``    ``printPath(res, nThNode, 1);``}` `// Driver Code``int` `main()``{``    ``// Given Node``    ``int` `nThNode = 7;` `    ``// Print path from root to all node.``    ``printPathToCoverAllNodeUtil(nThNode);` `    ``return` `0;``}`

Java

 `// Java program to print path from root to all``// nodes in a complete binary tree.``import` `java.util.*;` `class` `GFG``{` `// Function to print path of all the nodes``// nth node represent as given node``// kth node represents as left and right node``static` `void` `printPath(Vector res,``                    ``int` `nThNode, ``int` `kThNode)``{``    ``// base condition``    ``// if kth node value is greater``    ``// then nth node then its means``    ``// kth node is not valid so``    ``// we not store it into the res``    ``// simply we just return``    ``if` `(kThNode > nThNode)``        ``return``;` `    ``// Storing node into res``    ``res.add(kThNode);` `    ``// Print the path from root to node``    ``for` `(``int` `i = ``0``; i < res.size(); i++)``        ``System.out.print( res.get(i) + ``" "``);``    ``System.out.print( ``"\n"``);` `    ``// store left path of a tree``    ``// So for left we will go node(kThNode*2)``    ``printPath(res, nThNode, kThNode * ``2``);` `    ``// right path of a tree``    ``// and for right we will go node(kThNode*2+1)``    ``printPath(res, nThNode, kThNode * ``2` `+ ``1``);``    ` `    ``res.remove(res.size()-``1``);``}` `// Function to print path from root to all of the nodes``static` `void` `printPathToCoverAllNodeUtil(``int` `nThNode)``{``    ``// res is for store the path``    ``// from root to particulate node``    ``Vector res=``new` `Vector();` `    ``// Print path from root to all node.``    ``// third argument 1 because of we have``    ``// to consider root node is 1``    ``printPath(res, nThNode, ``1``);``}` `// Driver Code``public` `static` `void` `main(String args[])``{``    ``// Given Node``    ``int` `nThNode = ``7``;` `    ``// Print path from root to all node.``    ``printPathToCoverAllNodeUtil(nThNode);``}``}` `// This code is contributed by Arnab Kundu`

Python3

 `# Python3 program to print path from root``# to all nodes in a complete binary tree.` `# Function to print path of all the nodes``# nth node represent as given node kth``# node represents as left and right node``def` `printPath(res, nThNode, kThNode):` `    ``# base condition``    ``# if kth node value is greater``    ``# then nth node then its means``    ``# kth node is not valid so``    ``# we not store it into the res``    ``# simply we just return``    ``if` `kThNode > nThNode:``        ``return` `    ``# Storing node into res``    ``res.append(kThNode)` `    ``# Print the path from root to node``    ``for` `i ``in` `range``(``0``, ``len``(res)):``        ``print``(res[i], end ``=` `" "``)``    ``print``()` `    ``# store left path of a tree``    ``# So for left we will go node(kThNode*2)``    ``printPath(res[:], nThNode, kThNode ``*` `2``)` `    ``# right path of a tree``    ``# and for right we will go node(kThNode*2+1)``    ``printPath(res[:], nThNode, kThNode ``*` `2` `+` `1``)` `# Function to print path from root``# to all of the nodes``def` `printPathToCoverAllNodeUtil(nThNode):` `    ``# res is for store the path``    ``# from root to particulate node``    ``res ``=` `[]` `    ``# Print path from root to all node.``    ``# third argument 1 because of we have``    ``# to consider root node is 1``    ``printPath(res, nThNode, ``1``)` `# Driver Code``if` `__name__ ``=``=` `"__main__"``:` `    ``# Given Node``    ``nThNode ``=` `7` `    ``# Print path from root to all node.``    ``printPathToCoverAllNodeUtil(nThNode)` `# This code is contributed by Rituraj Jain`

C#

 `// C# program to print path from root to all``// nodes in a complete binary tree.``using` `System;``using` `System.Collections.Generic;` `class` `GFG``{` `// Function to print path of all the nodes``// nth node represent as given node``// kth node represents as left and right node``static` `void` `printPath(List<``int``> res,``                    ``int` `nThNode, ``int` `kThNode)``{``    ``// base condition``    ``// if kth node value is greater``    ``// then nth node then its means``    ``// kth node is not valid so``    ``// we not store it into the res``    ``// simply we just return``    ``if` `(kThNode > nThNode)``        ``return``;` `    ``// Storing node into res``    ``res.Add(kThNode);` `    ``// Print the path from root to node``    ``for` `(``int` `i = 0; i < res.Count; i++)``        ``Console.Write( res[i] + ``" "``);``    ``Console.Write( ``"\n"``);` `    ``// store left path of a tree``    ``// So for left we will go node(kThNode*2)``    ``printPath(res, nThNode, kThNode * 2);` `    ``// right path of a tree``    ``// and for right we will go node(kThNode*2+1)``    ``printPath(res, nThNode, kThNode * 2 + 1);``    ` `    ``res.RemoveAt(res.Count-1);``}` `// Function to print path from root to all of the nodes``static` `void` `printPathToCoverAllNodeUtil(``int` `nThNode)``{``    ``// res is for store the path``    ``// from root to particulate node``    ``List<``int``> res=``new` `List<``int``>();` `    ``// Print path from root to all node.``    ``// third argument 1 because of we have``    ``// to consider root node is 1``    ``printPath(res, nThNode, 1);``}` `// Driver Code``public` `static` `void` `Main(String []args)``{``    ``// Given Node``    ``int` `nThNode = 7;` `    ``// Print path from root to all node.``    ``printPathToCoverAllNodeUtil(nThNode);``}``}` `// This code contributed by Rajput-Ji`

PHP

 ` ``\$nThNode``)``        ``return``;` `    ``// Storing node into res``    ``array_push``(``\$res``, ``\$kThNode``);` `    ``// Print the path from root to node``    ``for` `(``\$i` `= 0; ``\$i` `< ``count``(``\$res``); ``\$i``++)``        ``echo` `\$res``[``\$i``] . ``" "``;``    ``echo` `"\n"``;` `    ``// store left path of a tree``    ``// So for left we will go node(kThNode*2)``    ``printPath(``\$res``, ``\$nThNode``, ``\$kThNode` `* 2);` `    ``// right path of a tree``    ``// and for right we will go node(kThNode*2+1)``    ``printPath(``\$res``, ``\$nThNode``, ``\$kThNode` `* 2 + 1);``}` `// Function to print path``// from root to all of the nodes``function` `printPathToCoverAllNodeUtil(``\$nThNode``)``{``    ``// res is for store the path``    ``// from root to particulate node``    ``\$res` `= ``array``();` `    ``// Print path from root to all node.``    ``// third argument 1 because of we have``    ``// to consider root node is 1``    ``printPath(``\$res``, ``\$nThNode``, 1);``}` `// Driver Code` `// Given Node``\$nThNode` `= 7;` `// Print path from root to all node.``printPathToCoverAllNodeUtil(``\$nThNode``);` `// This code is contributed by mits``?>`

Javascript

 ``

Output:

```1
1 2
1 2 4
1 2 5
1 3
1 3 6
1 3 7```

Time Complexity: O(N*H) where N is the number of nodes and H is the height of binary tree.
Auxiliary Space: O(H) where H is the height of binary tree.