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# Fibonacci Cube Graph

• Difficulty Level : Easy
• Last Updated : 30 Apr, 2021

You are given input as order of graph n (highest number of edges connected to a node), you have to find the number of vertices in a Fibonacci cube graph of order n.
Examples :

```Input : n = 3
Output : 5
Explanation :
Fib(n + 2) = Fib(5) = 5

Input : n = 2
Output : 3```

A Fibonacci Cube Graph is similar to hypercube graph, but with a fibonacci number of vertices. In fibonacci cube graph only 1 vertex has degree n rest all has degree less than n.
Fibonacci cube graph of order n has F(n + 2) vertices, where F(n) is a n-th fibonacci number
Fibonacii series : 1, 1, 2, 3, 5, 8, 13, 21, 34………………. For input n as order of graph, find the corresponding fibonacci number at the position n + 2.
where F(n) = F(n – 1) + F(n – 2)
Approach : Find the (n + 2)-th fibonacci number.
Below is the implementation of above approach :

## C++

 `// CPP code to find vertices in a fibonacci``// cube graph of order n``#include``using` `namespace` `std;` `// function to find fibonacci number``int` `fib(``int` `n)``{``    ``if` `(n <= 1)``        ``return` `n;``    ``return` `fib(n - 1) + fib(n - 2);``}` `// function for finding number of vertices``// in fibonacci cube graph``int` `findVertices (``int` `n)``{``    ``// return fibonacci number for f(n + 2)``    ``return` `fib(n + 2);``}` `// driver program``int` `main()``{``    ``// n is the order of the graph``    ``int` `n = 3;``    ``cout << findVertices(n);``    ``return` `0;``}`

## Java

 `// java code to find vertices in a fibonacci``// cube graph of order n``public` `class` `GFG {``    ` `    ``// function to find fibonacci number``    ``static` `int` `fib(``int` `n)``    ``{``        ``if` `(n <= ``1``)``            ``return` `n;``        ``return` `fib(n - ``1``) + fib(n - ``2``);``    ``}``    ` `    ``// function for finding number of vertices``    ``// in fibonacci cube graph``    ``static` `int` `findVertices (``int` `n)``    ``{``        ``// return fibonacci number for f(n + 2)``        ``return` `fib(n + ``2``);``    ``}``        ` `    ``public` `static` `void` `main(String args[]) {``        ` `        ``// n is the order of the graph``        ``int` `n = ``3``;``        ``System.out.println(findVertices(n));``    ``}``}` `// This code is contributed by Sam007`

## Python3

 `# Python3 code to find vertices in``# a fibonacci cube graph of order n` `# Function to find fibonacci number``def` `fib(n):` `    ``if` `n <``=` `1``:``        ``return` `n``        ` `    ``return` `fib(n ``-` `1``) ``+` `fib(n ``-` `2``)` `# Function for finding number of``# vertices in fibonacci cube graph``def` `findVertices(n):` `    ``# return fibonacci number``    ``# for f(n + 2)``    ``return` `fib(n ``+` `2``)` `# Driver Code``if` `__name__ ``=``=` `"__main__"``:` `    ``# n is the order of the graph``    ``n ``=` `3``    ``print``(findVertices(n))` `# This code is contributed``# by Rituraj Jain`

## C#

 `// C# code to find vertices in a fibonacci``// cube graph of order n``using` `System;` `class` `GFG {``    ` `    ``// function to find fibonacci number``    ``static` `int` `fib(``int` `n)``    ``{``        ``if` `(n <= 1)``            ``return` `n;``        ``return` `fib(n - 1) + fib(n - 2);``    ``}``    ` `    ``// function for finding number of``    ``// vertices in fibonacci cube graph``    ``static` `int` `findVertices (``int` `n)``    ``{``        ` `        ``// return fibonacci number for``        ``// f(n + 2)``        ``return` `fib(n + 2);``    ``}``    ` `    ``// Driver code``    ``static` `void` `Main()``    ``{``        ` `        ``// n is the order of the graph``        ``int` `n = 3;``        ` `        ``Console.Write(findVertices(n));``    ``}``}` `// This code is contributed by Sam007`

## PHP

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## Javascript

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Output :
`5`

Note that the above code can be optimized to work in O(Log n) using efficient implementations discussed in Program for Fibonacci numbers

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