Data commit

Task/Mind-boggling-card-trick/Python/mind-boggling-card-trick.py

@@ -0,0 +1,49 @@
+import random
+
+## 1. Cards
+n = 52
+Black, Red = 'Black', 'Red'
+blacks = [Black] * (n // 2)
+reds = [Red] * (n // 2)
+pack = blacks + reds
+# Give the pack a good shuffle.
+random.shuffle(pack)
+
+## 2. Deal from the randomised pack into three stacks
+black_stack, red_stack, discard = [], [], []
+while pack:
+    top = pack.pop()
+    if top == Black:
+        black_stack.append(pack.pop())
+    else:
+        red_stack.append(pack.pop())
+    discard.append(top)
+print('(Discards:', ' '.join(d[0] for d in discard), ')\n')
+
+## 3. Swap the same, random, number of cards between the two stacks.
+# We can't swap more than the number of cards in a stack.
+max_swaps = min(len(black_stack), len(red_stack))
+# Randomly choose the number of cards to swap.
+swap_count = random.randint(0, max_swaps)
+print('Swapping', swap_count)
+# Randomly choose that number of cards out of each stack to swap.
+def random_partition(stack, count):
+    "Partition the stack into 'count' randomly selected members and the rest"
+    sample = random.sample(stack, count)
+    rest = stack[::]
+    for card in sample:
+        rest.remove(card)
+    return rest, sample
+
+black_stack, black_swap = random_partition(black_stack, swap_count)
+red_stack, red_swap = random_partition(red_stack, swap_count)
+
+# Perform the swap.
+black_stack += red_swap
+red_stack += black_swap
+
+## 4. Order from randomness?
+if black_stack.count(Black) == red_stack.count(Red):
+    print('Yeha! The mathematicians assertion is correct.')
+else:
+    print('Whoops - The mathematicians (or my card manipulations) are flakey')