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-rw-r--r--scratch/facebook/hard/binary-adder.py22
1 files changed, 22 insertions, 0 deletions
diff --git a/scratch/facebook/hard/binary-adder.py b/scratch/facebook/hard/binary-adder.py
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index 000000000000..f79a9f22b38b
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+++ b/scratch/facebook/hard/binary-adder.py
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+import random
+
+def add(a, b):
+    """
+    Return the sum of `a` and `b`.
+    """
+    if b == 0:
+        return a
+    sum = a ^ b
+    carry = (a & b) << 1
+    return add(sum, carry)
+
+################################################################################
+# Tests
+################################################################################
+
+for _ in range(10):
+    x, y = random.randint(0, 100), random.randint(0, 100)
+    print("{} + {} = {} == {}".format(x, y, x + y, add(x, y)))
+    assert add(x, y) == x + y
+    print("Pass!")
+print("Success!")