day9 challenge

day9/day9.py

@@ -0,0 +1,50 @@
+#!/usr/bin/env python3
+import itertools
+
+
+def part1(inp):
+    preamble_size = 25
+    with open(inp) as infile:
+        cleanfile = (int(l.rstrip()) for l in infile)
+        for nums in window(cleanfile, preamble_size + 1):
+            candidate = nums[-1]
+            if not test_number(candidate, nums[:-1]):
+                return candidate
+    return -1
+
+
+def window(seq, n):
+    it = iter(seq)
+    result = tuple(itertools.islice(it, n))
+    if len(result) == n:
+        yield result
+    for elem in it:
+        result = result[1:] + (elem,)
+        yield result
+
+
+def test_number(num, previous):
+    sums = set(sum(x) for x in itertools.combinations(previous, 2))
+    return num in sums
+
+
+def part2(infile, target: int):
+    lines = [int(l.rstrip()) for l in open(infile).readlines()]
+    total = 0
+    visited = []
+    for index, _ in enumerate(lines):
+        i = index
+        while total < target:
+            total += lines[i]
+            visited.append(lines[i])
+            i += 1
+            if total == target:
+                return max(visited) + min(visited)
+        visited.clear()
+        total = 0
+
+
+if __name__ == "__main__":
+    invalid_number = part1("input.txt")
+    print("part1 ", invalid_number)
+    print("part2 ", part2("input.txt", invalid_number))