Finding the N'th number in the Fibonacci sequence

Generating n’th Fibonacci Number.

What is a Fibonacci Sequence
The Fibonacci sequence starts with the numbers 0 followed by 1. The subsequent number is the addition of the previous two numbers. Thus the Fibonaaic sequence looks like below
0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, and so on.

Note : Generating the n’th number in Fibonacci sequence using recursion is very inefficient as we come across numerous overlapping sub-problems. A better idea is to use an iterative or dynamic programming approach.


Algorithm : Finding the n’th Fibonacci number
FibonacciNumber ( n )
1.   If n is 0 or 1
2.       return n
3.   Else return the sum of the previous two Fibonacci numbers.
4.       return FibonacciNumber (n-1) + FibonacciNumber (n-2)


C++

C++ : Finding the N'th Fibonacci number implemented in C++14


Python : Finding the n’th Fibonacci number implemented in Python3

def Fibonacci (n) :

    if n <= 1  :
       return n 

    return Fibonacci (n-1) + Fibonacci (n-2)
    
def main() :
    n = int(input("Finding n'th Fibonacci(n) number. Enter n : ")) 
    if n <= 1 : 
        print(n, end = ' ')
    else :
        print(int(Fibonacci(n)))

if __name__ == "__main__" :
    main()

Output of finding the n’th Fibonacci number implemented in Python3

Finding n'th Fibonacci(n) number. Enter n : 10
55
Finding n'th Fibonacci(n) number. Enter n : 2
1
Finding n'th Fibonacci(n) number. Enter n : 11
89
Finding n'th Fibonacci(n) number. Enter n : 12
144

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