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Challenge 3: Fibonacci Sequence

curriculum/challenges/english/blocks/daily-coding-challenges-python/681cb1a2dab50c87ddb2e514.md

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--description--

The Fibonacci sequence is a series of numbers where each number is the sum of the two preceding ones. When starting with 0 and 1, the first 10 numbers in the sequence are 0, 1, 1, 2, 3, 5, 8, 13, 21, 34.

Given an array containing the first two numbers of a Fibonacci sequence, and an integer representing the length of the sequence, return an array containing the sequence of the given length.

  • Your function should handle sequences of any length greater than or equal to zero.
  • If the length is zero, return an empty array.
  • Note that the starting numbers are part of the sequence.

--hints--

fibonacci_sequence([0, 1], 20) should return [0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, 233, 377, 610, 987, 1597, 2584, 4181].

js
({test: () => { runPython(`
from unittest import TestCase
TestCase().assertEqual(fibonacci_sequence([0, 1], 20), [0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, 233, 377, 610, 987, 1597, 2584, 4181])`)
}})

fibonacci_sequence([21, 32], 1) should return [21].

js
({test: () => { runPython(`
from unittest import TestCase
TestCase().assertEqual(fibonacci_sequence([21, 32], 1), [21])`)
}})

fibonacci_sequence([0, 1], 0) should return [].

js
({test: () => { runPython(`
from unittest import TestCase
TestCase().assertEqual(fibonacci_sequence([0, 1], 0), [])`)
}})

fibonacci_sequence([10, 20], 2) should return [10, 20].

js
({test: () => { runPython(`
from unittest import TestCase
TestCase().assertEqual(fibonacci_sequence([10, 20], 2), [10, 20])`)
}})

fibonacci_sequence([123456789, 987654321], 5) should return [123456789, 987654321, 1111111110, 2098765431, 3209876541].

js
({test: () => { runPython(`
from unittest import TestCase
TestCase().assertEqual(fibonacci_sequence([123456789, 987654321], 5), [123456789, 987654321, 1111111110, 2098765431, 3209876541])`)
}})

--seed--

--seed-contents--

py
def fibonacci_sequence(start_sequence, length):

    return length

--solutions--

py
def fibonacci_sequence(start_sequence, length):
    if length == 0:
        return []
    if length == 1:
        return [start_sequence[0]]
    if length == 2:
        return start_sequence[:]

    sequence = start_sequence[:]
    while len(sequence) < length:
        next_value = sequence[-1] + sequence[-2]
        sequence.append(next_value)

    return sequence