Advent of Code 2025 - Day 3 : Python version

advent_of_code/2025(python)/day3.py

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+import heapq
+
+
+def solve_day3_part1(input_):
+    res = 0
+    for line in input_:
+        rel = {}
+        max_ch, second_max_ch = '', ''
+        for i, ch in enumerate(line):
+            rel[ch] = i
+            if max_ch == '' or (ch > max_ch and i < len(line)-1):
+                second_max_ch = ''
+                max_ch = ch
+            elif second_max_ch == '' or ch > second_max_ch:
+                second_max_ch = ch
+
+        if rel[max_ch] < rel[second_max_ch]:
+            res += int(f"{max_ch}{second_max_ch}")
+        else:
+            res += int(f"{second_max_ch}{max_ch}")
+
+    return res
+
+
+def solve_day3_part2(input_):
+    res = 0
+    for line in input_:
+        # construct a priority-queue, sort based on (largest, left-most) order
+        pq = []
+        for i, ch in enumerate(line):
+            pq.append((-1*int(ch), -1*(len(line)-i)))
+
+        numbers = 12
+        powers = ""
+        prev_index = float('inf')
+        heapq.heapify(pq)
+        while numbers > 0:
+            invalid_item = []
+            while True:
+                curr = heapq.heappop(pq)
+                if -1*curr[1] >= numbers and -1*(curr[1]) < prev_index:
+                    powers += str(-1*curr[0])
+                    prev_index = -1*curr[1]
+                    break
+                else:
+                    invalid_item.append(curr)
+
+            # add original back
+            for item in invalid_item:
+                heapq.heappush(pq, item)
+            numbers -= 1
+
+        res += int(powers)
+
+    return res

advent_of_code/2025(python)/test_day3.py

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+import unittest
+
+from day3 import solve_day3_part1, solve_day3_part2
+
+question_input = [
+    "987654321111111",
+    "811111111111119",
+    "234234234234278",
+    "818181911112111",
+]
+
+
+class TestSample(unittest.TestCase):
+
+    def test_part1(self):
+        self.assertEqual(solve_day3_part1(question_input), 357)
+
+    def test_part2(self):
+        self.assertEqual(solve_day3_part2(question_input), 3121910778619)
+
+
+if __name__ == "__main__":
+    unittest.main()