Solve 2021 day 3

2021/03_diagnostic.py

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+#!/usr/bin/env python3
+import sys
+
+def common(diag, i):
+    return int(sum(n >> i & 1 for n in diag) / len(diag) + .5)
+
+def gamma(diag, width):
+    return sum(common(diag, i) << i for i in range(width))
+
+def epsilon(diag, width):
+    return sum((1 - common(diag, i)) << i for i in range(width))
+
+def rating(diag, width, most_common):
+    i = width - 1
+    while len(diag) > 1:
+        bit = common(diag, i) ^ most_common
+        diag = [n for n in diag if n >> i & 1 == bit]
+        i -= 1
+    return diag[0]
+
+def oxygen(diag, width):
+    return rating(diag, width, True)
+
+def co2_scrub(diag, width):
+    return rating(diag, width, False)
+
+diag = [int(line, 2) for line in sys.stdin]
+width = max(n.bit_length() for n in diag)
+print(gamma(diag, width) * epsilon(diag, width))
+print(oxygen(diag, width) * co2_scrub(diag, width))

2021/input/3

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