Initial commit with days 1, 2, and 3

Signed-off-by: Alek Ratzloff <alekratz@gmail.com>

day03/day03.py

@@ -0,0 +1,70 @@
+#!/usr/bin/env python3
+import copy
+import sys
+from typing import Sequence
+
+
+def part1(lines: Sequence[int], bits=12):
+    gamma = 0
+    epsilon = 0
+    for bit in range(bits):
+        mask = 1 << (bits - bit - 1)
+        ones = 0
+        for line in lines:
+            if mask & line:
+                ones += 1
+        zeroes = len(lines) - ones
+        if ones > zeroes:
+            gamma |= mask
+        else:
+            epsilon |= mask
+    # Fun thing - epsilon rate is just the inversion of the gamma rate.
+    # However, python doesn't seem to support signed inversion so we just calculate it above. boo
+    print(f"gamma: {gamma} {bin(gamma)}")
+    print(f"epsilon: {epsilon} {bin(epsilon)}")
+    print(f"product: {gamma * epsilon}")
+
+
+def part2(lines: Sequence[int], bits=12):
+    oxygen = copy.deepcopy(lines)
+    carbon = copy.deepcopy(lines)
+    for bit in range(bits):
+        # Find the most common bit
+        if len(oxygen) > 1:
+            mask = 1 << (bits - bit - 1)
+            ones = 0
+            for line in oxygen:
+                if mask & line:
+                    ones += 1
+            zeroes = len(oxygen) - ones
+            if ones >= zeroes:
+                # Filter out oxygen numbers that don't have a 1 in this position
+                oxygen = [line for line in oxygen if line & mask]
+            else:
+                oxygen = [line for line in oxygen if not (line & mask)]
+
+        # Now do this on the carbon array
+        if len(carbon) > 1:
+            ones = 0
+            for line in carbon:
+                if mask & line:
+                    ones += 1
+            zeroes = len(carbon) - ones
+            if ones >= zeroes:
+                # Keep the *least* common
+                carbon = [line for line in carbon if not (line & mask)]
+            else:
+                carbon = [line for line in carbon if line & mask]
+    oxygen, = oxygen
+    carbon, = carbon
+    print(f"Oxygen: {oxygen}")
+    print(f"Carbon: {carbon}")
+    print(f"Product: {oxygen * carbon}")
+
+
+lines = [int(line, 2) for line in sys.stdin]
+
+print("Part 1")
+part1(lines)
+print("Part 2")
+part2(lines)