FibonacciNumber.py

# Source : https://leetcode.com/problems/fibonacci-number
# Author : Hamza Mogni
# Date   : 2022-01-20

#####################################################################################################
#
# The Fibonacci numbers, commonly denoted F(n) form a sequence, called the Fibonacci sequence, such
# that each number is the sum of the two preceding ones, starting from 0 and 1. That is,
#
# F(0) = 0, F(1) = 1
# F(n) = F(n - 1) + F(n - 2), for n > 1.
#
# Given n, calculate F(n).
#
# Example 1:
#
# Input: n = 2
# Output: 1
# Explanation: F(2) = F(1) + F(0) = 1 + 0 = 1.
#
# Example 2:
#
# Input: n = 3
# Output: 2
# Explanation: F(3) = F(2) + F(1) = 1 + 1 = 2.
#
# Example 3:
#
# Input: n = 4
# Output: 3
# Explanation: F(4) = F(3) + F(2) = 2 + 1 = 3.
#
# Constraints:
#
# 	0 <= n <= 30
#####################################################################################################

class Solution:
    def fib(self, n: int) -> int:
        first = 0
        second = 1

        if n == 0:
            return first
        elif n == 1:
            return second
        else:
            for a in range(2, n+1):
                nbr = first + second

                first = second
                second = nbr

            return nbr


s = Solution()
print(s.fib(9))