cleaning up and organizing old problems (builtin)

src/builtin_structures/fibonacci.py

@@ -0,0 +1,44 @@
+#!/usr/bin/env python
+
+__author__ = "bt3"
+
+
+def fib_generator():
+    a, b = 0, 1
+
+    while True:
+        yield b
+        a, b = b, a+b
+
+
+def fib(n):
+    '''
+    >>> fib(2)
+    1
+    >>> fib(5)
+    5
+    >>> fib(7)
+    13
+    '''
+    if n < 3:
+        return 1
+
+    a, b = 0, 1
+    count = 1
+
+    while count < n:
+        count += 1
+        a, b = b, a+b
+
+    return b
+
+
+if __name__ == '__main__':
+    import doctest
+    doctest.testmod()
+
+    fib = fib_generator()
+    print(next(fib))
+    print(next(fib))
+    print(next(fib))
+    print(next(fib))