add fibonacci (#35)

* add fibonacci

* Formatted with psf/black

Co-authored-by: github-actions <${GITHUB_ACTOR}@users.noreply.github.com>

Author: realDuYuanChao

maths/fibonacci.py

@@ -0,0 +1,34 @@
+def fibonacci(number: int) -> int:
+    """
+    >>> fibonacci(0)
+    0
+    >>> fibonacci(1)
+    1
+    >>> fibonacci(2)
+    1
+    >>> fibonacci(3)
+    2
+    >>> fibonacci(4)
+    3
+    >>> fibonacci(5)
+    5
+    >>> fibonacci(6)
+    8
+    >>> fibonacci(7)
+    13
+    >>> fibonacci(8)
+    21
+    """
+    first_item = 0
+    second_item = 1
+    for i in range(0, number):
+        temp = first_item + second_item
+        first_item = second_item
+        second_item = temp
+    return first_item
+
+
+if __name__ == "__main__":
+    from doctest import testmod
+
+    testmod()

maths/fibonacci_recursion.py

@@ -0,0 +1,32 @@
+def fibonacci(number: int) -> int:
+    """
+    >>> fibonacci(0)
+    0
+    >>> fibonacci(1)
+    1
+    >>> fibonacci(2)
+    1
+    >>> fibonacci(3)
+    2
+    >>> fibonacci(4)
+    3
+    >>> fibonacci(5)
+    5
+    >>> fibonacci(6)
+    8
+    >>> fibonacci(7)
+    13
+    >>> fibonacci(8)
+    21
+    """
+    return (
+        number
+        if number == 0 or number == 1
+        else fibonacci(number - 1) + fibonacci(number - 2)
+    )
+
+
+if __name__ == "__main__":
+    from doctest import testmod
+
+    testmod()

maths/fibonacci_with_list.py

@@ -0,0 +1,33 @@
+def fibonacci(number: int) -> int:
+    """
+    >>> fibonacci(0)
+    0
+    >>> fibonacci(1)
+    1
+    >>> fibonacci(2)
+    1
+    >>> fibonacci(3)
+    2
+    >>> fibonacci(4)
+    3
+    >>> fibonacci(5)
+    5
+    >>> fibonacci(6)
+    8
+    >>> fibonacci(7)
+    13
+    >>> fibonacci(8)
+    21
+    """
+    fibs = [0] * (number + 2)
+    fibs[0] = 0
+    fibs[1] = 1
+    for i in range(2, number + 1):
+        fibs[i] = fibs[i - 1] + fibs[i - 2]
+    return fibs[number]
+
+
+if __name__ == "__main__":
+    from doctest import testmod
+
+    testmod()