# Print all the levels with odd and even number of nodes in it | Set-2

• Last Updated : 10 Aug, 2021

Given an N-ary tree, print all the levels with odd and even number of nodes in it.

Examples

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```For example consider the following tree
1               - Level 1
/     \
2       3           - Level 2
/   \       \
4     5       6        - Level 3
/  \     /
7    8   9         - Level 4

The levels with odd number of nodes are: 1 3 4
The levels with even number of nodes are: 2```

Note: The level numbers starts from 1. That is, the root node is at the level 1.

Approach

• Insert all the connecting nodes to a 2-D vector tree.
• Run a BFS on the tree such that height[node] = 1 + height[parent]
• Once BFS traversal is completed, increase the count[] array by 1, for every node’s level.
• Iterate from first level to last level, and print all nodes with count[] values as odd to get level with odd number nodes.
• Iterate from first level to last level, and print all nodes with count[] values as even to get level with even number nodes.

Below is the implementation of the above approach:

## C++

 `// C++ program to print all levels``// with odd and even number of nodes` `#include ``using` `namespace` `std;` `// Function for BFS in a tree``void` `bfs(``int` `node, ``int` `parent, ``int` `height[], ``int` `vis[],``         ``vector<``int``> tree[])``{` `    ``// mark first node as visited``    ``vis[node] = 1;` `    ``// Declare Queue``    ``queue<``int``> q;` `    ``// Push the first element``    ``q.push(1);` `    ``// calculate the level of every node``    ``height[node] = 1 + height[parent];` `    ``// Check if the queue is empty or not``    ``while` `(!q.empty()) {` `        ``// Get the top element in the queue``        ``int` `top = q.front();` `        ``// pop the element``        ``q.pop();` `        ``// mark as visited``        ``vis[top] = 1;` `        ``// Iterate for the connected nodes``        ``for` `(``int` `i = 0; i < tree[top].size(); i++) {` `            ``// if not visited``            ``if` `(!vis[tree[top][i]]) {` `                ``// Insert into queue``                ``q.push(tree[top][i]);` `                ``// Increase level``                ``height[tree[top][i]] = 1 + height[top];``            ``}``        ``}``    ``}``}` `// Function to insert edges``void` `insertEdges(``int` `x, ``int` `y, vector<``int``> tree[])``{``    ``tree[x].push_back(y);``    ``tree[y].push_back(x);``}` `// Function to print all levels``void` `printLevelsOddEven(``int` `N, ``int` `vis[], ``int` `height[])``{``    ``int` `mark[N + 1];``    ``memset``(mark, 0, ``sizeof` `mark);` `    ``int` `maxLevel = 0;``    ``for` `(``int` `i = 1; i <= N; i++) {` `        ``// count number of nodes``        ``// in every level``        ``if` `(vis[i])``            ``mark[height[i]]++;` `        ``// find the maximum height of tree``        ``maxLevel = max(height[i], maxLevel);``    ``}` `    ``// print odd number of nodes``    ``cout << ``"The levels with odd number of nodes are: "``;``    ``for` `(``int` `i = 1; i <= maxLevel; i++) {``        ``if` `(mark[i] % 2)``            ``cout << i << ``" "``;``    ``}` `    ``// print even number of nodes``    ``cout << ``"\nThe levels with even number of nodes are: "``;``    ``for` `(``int` `i = 1; i <= maxLevel; i++) {``        ``if` `(mark[i] % 2 == 0)``            ``cout << i << ``" "``;``    ``}``}` `// Driver Code``int` `main()``{``    ``// Construct the tree` `    ``/*   1``       ``/   \``      ``2     3``     ``/ \     \``    ``4    5    6``        ``/ \  /``       ``7   8 9  */` `    ``const` `int` `N = 9;` `    ``vector<``int``> tree[N + 1];` `    ``insertEdges(1, 2, tree);``    ``insertEdges(1, 3, tree);``    ``insertEdges(2, 4, tree);``    ``insertEdges(2, 5, tree);``    ``insertEdges(5, 7, tree);``    ``insertEdges(5, 8, tree);``    ``insertEdges(3, 6, tree);``    ``insertEdges(6, 9, tree);` `    ``int` `height[N + 1];``    ``int` `vis[N + 1] = { 0 };` `    ``// call the bfs function``    ``bfs(1, 0, height, vis, tree);` `    ``// Function to print``    ``printLevelsOddEven(N, vis, height);` `    ``return` `0;``}`

## Java

 `// Java program to print all levels``// with odd and even number of nodes``import` `java.util.*;``public` `class` `Main``{``    ``// Function for BFS in a tree``    ``static` `void` `bfs(``int` `node, ``int` `parent, ``int``[] height, ``int``[] vis, Vector> tree)``    ``{``        ``// Mark first node as visited``        ``vis[node] = ``1``;``      ` `        ``// Declare Queue``        ``Queue q = ``new` `LinkedList<>();``      ` `        ``// Push the first element``        ``q.add(``1``);``      ` `        ``// Calculate the level of every node``        ``height[node] = ``1` `+ height[parent];``      ` `        ``// Check if the queue is empty or not``        ``while` `(q.size() != ``0``)``        ``{``             ` `            ``// Get the top element in the queue``            ``int` `top = (``int``)q.peek();``      ` `            ``// Pop the element``            ``q.remove();``      ` `            ``// Mark as visited``            ``vis[top] = ``1``;``      ` `            ``// Iterate for the connected nodes``            ``for``(``int` `i = ``0``; i < tree.get(top).size(); i++)``            ``{``                 ` `                ``// If not visited``                ``if` `(vis[(``int``)tree.get(top).get(i)] == ``0``)``                ``{``                     ` `                    ``// Insert into queue``                    ``q.add(tree.get(top).get(i));``      ` `                    ``// Increase level``                    ``height[(``int``)tree.get(top).get(i)] = ``1` `+ height[top];``                ``}``            ``}``        ``}``    ``}``      ` `    ``// Function to insert edges``    ``static` `void` `insertEdges(``int` `x, ``int` `y, Vector> tree)``    ``{``        ``tree.get(x).add(y);``        ``tree.get(y).add(x);``    ``}``      ` `    ``// Function to print all levels``    ``static` `void` `printLevelsOddEven(``int` `N, ``int``[] vis, ``int``[] height)``    ``{``        ``int``[] mark = ``new` `int``[N + ``1``];``        ``for``(``int` `i = ``0``; i < N + ``1``; i++)``        ``{``            ``mark[i] = ``0``;``        ``}``      ` `        ``int` `maxLevel = ``0``;``        ``for``(``int` `i = ``1``; i <= N; i++)``        ``{``             ` `            ``// Count number of nodes``            ``// in every level``            ``if` `(vis[i]!=``0``)``                ``mark[height[i]]++;``      ` `            ``// Find the maximum height of tree``            ``maxLevel = Math.max(height[i], maxLevel);``        ``}``      ` `        ``// Print odd number of nodes``        ``System.out.print(``"The levels with odd "` `+``                      ``"number of nodes are: "``);``         ` `        ``for``(``int` `i = ``1``; i <= maxLevel; i++)``        ``{``            ``if` `(mark[i] % ``2` `!= ``0``)``            ``{``                ``System.out.print(i + ``" "``);``            ``}``        ``}``      ` `        ``// print even number of nodes``        ``System.out.println();``        ``System.out.print(``"The levels with even "` `+``                      ``"number of nodes are: "``);``         ` `        ``for``(``int` `i = ``1``; i <= maxLevel; i++)``        ``{``            ``if` `(mark[i] % ``2` `== ``0``)``            ``{``                ``System.out.print(i + ``" "``);``            ``}``        ``}``    ``}` `    ``public` `static` `void` `main(String[] args) {``        ``// Construct the tree``     ` `        ``/*   1``           ``/   \``          ``2     3``         ``/ \     \``        ``4    5    6``            ``/ \  /``           ``7   8 9  */``         ` `        ``int` `N = ``9``;``         ` `        ``Vector> tree = ``new` `Vector>();``         ` `        ``for``(``int` `i = ``0``; i < N + ``1``; i++)``        ``{``            ``tree.add(``new` `Vector());``        ``}``         ` `        ``insertEdges(``1``, ``2``, tree);``        ``insertEdges(``1``, ``3``, tree);``        ``insertEdges(``2``, ``4``, tree);``        ``insertEdges(``2``, ``5``, tree);``        ``insertEdges(``5``, ``7``, tree);``        ``insertEdges(``5``, ``8``, tree);``        ``insertEdges(``3``, ``6``, tree);``        ``insertEdges(``6``, ``9``, tree);``         ` `        ``int``[] height = ``new` `int``[N + ``1``];``        ``int``[] vis = ``new` `int``[N + ``1``];``        ``for``(``int` `i = ``0``; i < N + ``1``; i++)``        ``{``            ``vis[i] = ``0``;``        ``}``         ` `        ``height[``0``] = ``0``;``         ` `        ``// Call the bfs function``        ``bfs(``1``, ``0``, height, vis, tree);``         ` `        ``// Function to print``        ``printLevelsOddEven(N, vis, height);``    ``}``}` `// This code is contributed by divyeshrabadiya07.`

## Python3

 `# Python3 program to print all levels``# with odd and even number of nodes` `# Function for BFS in a tree``def` `bfs(node, parent, height, vis, tree):` `    ``# mark first node as visited``    ``vis[node] ``=` `1` `    ``# Declare Queue``    ``q ``=` `[]` `    ``# append the first element``    ``q.append(``1``)` `    ``# calculate the level of every node``    ``height[node] ``=` `1` `+` `height[parent]` `    ``# Check if the queue is empty or not``    ``while` `(``len``(q)):` `        ``# Get the top element in``        ``# the queue``        ``top ``=` `q[``0``]` `        ``# pop the element``        ``q.pop(``0``)` `        ``# mark as visited``        ``vis[top] ``=` `1` `        ``# Iterate for the connected nodes``        ``for` `i ``in` `range``(``len``(tree[top])):``            ` `            ``# if not visited``            ``if` `(``not` `vis[tree[top][i]]):` `                ``# Insert into queue``                ``q.append(tree[top][i])` `                ``# Increase level``                ``height[tree[top][i]] ``=` `1` `+` `height[top]` `# Function to insert edges``def` `insertEdges(x, y, tree):` `    ``tree[x].append(y)``    ``tree[y].append(x)``    ` `# Function to print all levels``def` `printLevelsOddEven(N, vis, height):` `    ``mark ``=` `[``0``] ``*` `(N ``+` `1``)` `    ``maxLevel ``=` `0``    ``for` `i ``in` `range``(``1``, N ``+` `1``):` `        ``# count number of nodes``        ``# in every level``        ``if` `(vis[i]) :``            ``mark[height[i]] ``+``=` `1` `        ``# find the maximum height of tree``        ``maxLevel ``=` `max``(height[i], maxLevel)``    ` `    ``# prodd number of nodes``    ``print``(``"The levels with odd number"``,``          ``"of nodes are:"``, end ``=` `" "``)``    ``for` `i ``in` `range``(``1``, maxLevel ``+` `1``):``        ``if` `(mark[i] ``%` `2``):``            ``print``(i, end ``=` `" "` `)``    ` `    ``# print even number of nodes``    ``print``(``"\nThe levels with even number"``,``            ``"of nodes are:"``, end ``=` `" "``)``    ``for` `i ``in` `range``(``1``, maxLevel ):``        ``if` `(mark[i] ``%` `2` `=``=` `0``):``            ``print``(i, end ``=` `" "``)` `# Driver Code``if` `__name__ ``=``=` `'__main__'``:``    ` `    ``# Construct the tree``    ``""" 1``    ``/ \``    ``2 3``    ``/ \ \``    ``4 5 6``        ``/ \ /``    ``7 8 9 """` `    ``N ``=` `9` `    ``tree ``=` `[[``0``]] ``*` `(N ``+` `1``)` `    ``insertEdges(``1``, ``2``, tree)``    ``insertEdges(``1``, ``3``, tree)``    ``insertEdges(``2``, ``4``, tree)``    ``insertEdges(``2``, ``5``, tree)``    ``insertEdges(``5``, ``7``, tree)``    ``insertEdges(``5``, ``8``, tree)``    ``insertEdges(``3``, ``6``, tree)``    ``insertEdges(``6``, ``9``, tree)` `    ``height ``=` `[``0``] ``*` `(N ``+` `1``)``    ``vis ``=` `[``0``] ``*` `(N ``+` `1``)` `    ``# call the bfs function``    ``bfs(``1``, ``0``, height, vis, tree)` `    ``# Function to pr``    ``printLevelsOddEven(N, vis, height)` `# This code is contributed``# by SHUBHAMSINGH10`

## C#

 `// C# program to print all levels``// with odd and even number of nodes``using` `System;``using` `System.Collections;` `class` `GFG{` `// Function for BFS in a tree``static` `void` `bfs(``int` `node, ``int` `parent,``                ``int` `[]height, ``int` `[]vis,``                ``ArrayList []tree)``{``    ` `    ``// Mark first node as visited``    ``vis[node] = 1;`` ` `    ``// Declare Queue``    ``Queue q = ``new` `Queue();`` ` `    ``// Push the first element``    ``q.Enqueue(1);`` ` `    ``// Calculate the level of every node``    ``height[node] = 1 + height[parent];`` ` `    ``// Check if the queue is empty or not``    ``while` `(q.Count != 0)``    ``{``        ` `        ``// Get the top element in the queue``        ``int` `top = (``int``)q.Peek();`` ` `        ``// Pop the element``        ``q.Dequeue();`` ` `        ``// Mark as visited``        ``vis[top] = 1;`` ` `        ``// Iterate for the connected nodes``        ``for``(``int` `i = 0; i < tree[top].Count; i++)``        ``{``            ` `            ``// If not visited``            ``if` `(vis[(``int``)tree[top][i]] == 0)``            ``{``                ` `                ``// Insert into queue``                ``q.Enqueue(tree[top][i]);`` ` `                ``// Increase level``                ``height[(``int``)tree[top][i]] = 1 + height[top];``            ``}``        ``}``    ``}``}`` ` `// Function to insert edges``static` `void` `insertEdges(``int` `x, ``int` `y, ArrayList []tree)``{``    ``tree[x].Add(y);``    ``tree[y].Add(x);``}`` ` `// Function to print all levels``static` `void` `printLevelsOddEven(``int` `N, ``int` `[]vis,``                               ``int` `[]height)``{``    ``int` `[]mark = ``new` `int``[N + 1];``    ``Array.Fill(mark, 0);`` ` `    ``int` `maxLevel = 0;``    ``for``(``int` `i = 1; i <= N; i++)``    ``{``        ` `        ``// Count number of nodes``        ``// in every level``        ``if` `(vis[i]!=0)``            ``mark[height[i]]++;`` ` `        ``// Find the maximum height of tree``        ``maxLevel = Math.Max(height[i], maxLevel);``    ``}`` ` `    ``// Print odd number of nodes``    ``Console.Write(``"The levels with odd "` `+``                  ``"number of nodes are: "``);``    ` `    ``for``(``int` `i = 1; i <= maxLevel; i++)``    ``{``        ``if` `(mark[i] % 2 != 0)``        ``{``            ``Console.Write(i + ``" "``);``        ``}``    ``}`` ` `    ``// print even number of nodes``    ``Console.Write(``"\nThe levels with even "` `+``                  ``"number of nodes are: "``);``    ` `    ``for``(``int` `i = 1; i <= maxLevel; i++)``    ``{``        ``if` `(mark[i] % 2 == 0)``        ``{``            ``Console.Write(i + ``" "``);``        ``}``    ``}``}``    ` `// Driver code   ``static` `void` `Main()``{``      ` `    ``// Construct the tree``    ` `    ``/*   1``       ``/   \``      ``2     3``     ``/ \     \``    ``4    5    6``        ``/ \  /``       ``7   8 9  */``    ` `    ``int` `N = 9;``    ` `    ``ArrayList []tree = ``new` `ArrayList[N + 1];``    ` `    ``for``(``int` `i = 0; i < N + 1; i++)``    ``{``        ``tree[i] = ``new` `ArrayList();``    ``}``    ` `    ``insertEdges(1, 2, tree);``    ``insertEdges(1, 3, tree);``    ``insertEdges(2, 4, tree);``    ``insertEdges(2, 5, tree);``    ``insertEdges(5, 7, tree);``    ``insertEdges(5, 8, tree);``    ``insertEdges(3, 6, tree);``    ``insertEdges(6, 9, tree);``    ` `    ``int` `[]height = ``new` `int``[N + 1];``    ``int` `[]vis = ``new` `int``[N + 1];``    ``Array.Fill(vis, 0);``    ` `    ``height = 0;``    ` `    ``// Call the bfs function``    ``bfs(1, 0, height, vis, tree);``    ` `    ``// Function to print``    ``printLevelsOddEven(N, vis, height);``}``}` `// This code is contributed by rutvik_56`

## Javascript

 ``
Output:
```The levels with odd number of nodes are: 1 3 4
The levels with even number of nodes are: 2```

Time Complexity: O(N)
Auxiliary Space: O(N)

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