add collatz exercise, simplify names, update readme

collatz/collatz.py

@@ -0,0 +1,30 @@
+import readline
+
+class CollatzCalculator:
+    def calculate_steps(self, n: int) -> int:
+        if n <= 1:
+            return 0
+        steps = 0
+        while n != 1:
+            if n % 2 == 0:
+                n //= 2
+                print(f"Step #{steps + 1}: even, divide by 2 -> {n}")
+            else:
+                n = 3 * n + 1
+                print(f"Step #{steps + 1}: odd, multiply by 3 and add 1 -> {n}")
+            steps += 1
+        return steps + 1
+
+def main():
+    calculator = CollatzCalculator()
+    while True:
+        try:
+            n = input("Please enter a whole number: ")
+            print(f"Result: {calculator.calculate_steps(int(n))} steps needed to reach {n}")
+        except ValueError:
+            print("ERROR: integer required")
+        except (EOFError, KeyboardInterrupt):
+            break
+
+if __name__ == "__main__":
+    main()

collatz/test_collatz.py

@@ -0,0 +1,27 @@
+import pytest
+from collatz import CollatzCalculator
+
+def test_calculate_steps_for_1():
+    calc = CollatzCalculator()
+    assert calc.calculate_steps(1) == 0
+
+def test_calculate_steps_for_2():
+    calc = CollatzCalculator()
+    assert calc.calculate_steps(2) == 2  # 2 -> 1 (even), returns 2 steps
+
+def test_calculate_steps_for_3():
+    calc = CollatzCalculator()
+    assert calc.calculate_steps(3) == 8  # 3 -> 10 -> 5 -> 16 -> 8 -> 4 -> 2 -> 1
+
+def test_calculate_steps_for_6():
+    calc = CollatzCalculator()
+    assert calc.calculate_steps(6) == 9  # 6 -> 3 -> 10 -> 5 -> 16 -> 8 -> 4 -> 2 -> 1
+
+def test_calculate_steps_for_large_number():
+    calc = CollatzCalculator()
+    assert calc.calculate_steps(27) == 112
+
+def test_calculate_steps_for_zero_and_negative():
+    calc = CollatzCalculator()
+    assert calc.calculate_steps(0) == 0
+    assert calc.calculate_steps(-5) == 0