[Sync Iteration] python/collatz-conjecture/2

solutions/python/collatz-conjecture/2/collatz_conjecture.py

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+"""
+Collatz Conjecture.
+
+The rules were deceptively simple. Pick any positive integer.
+
+If it's even, divide it by 2.
+If it's odd, multiply it by 3 and add 1.
+Then, repeat these steps with the result, continuing indefinitely.
+
+Curious, you picked number 12 to test and began the journey:
+
+12 ➜ 6 ➜ 3 ➜ 10 ➜ 5 ➜ 16 ➜ 8 ➜ 4 ➜ 2 ➜ 1
+"""
+
+
+def steps(number: int) -> int:
+    """
+    Return the number of steps it takes to reach 1 according to
+    the rules of the Collatz Conjecture.
+
+    :param number: any positive integer
+    :type number: int
+    :return: number of steps it takes to reach 1
+    :rtype: int
+    """
+    if number < 1:
+        raise ValueError("Only positive integers are allowed")
+
+    n_steps: int = 0
+    while number > 1:
+        # If it's even, divide it by 2
+        if number % 2 == 0:
+            # Switch to integer division
+            # keeps everything as int and avoids precision issues
+            number = number // 2
+        # If it's odd, multiply it by 3 and add 1
+        else:
+            number = (number * 3) + 1
+        n_steps += 1
+
+    return n_steps