Add Day 7 solution.

day7/solver.py

@@ -0,0 +1,69 @@
+"""
+Bit tired and lazy today.
+
+Just going to go for minimal effort.
+"""
+import sys
+
+test_data = r"""
+190: 10 19
+3267: 81 40 27
+83: 17 5
+156: 15 6
+7290: 6 8 6 15
+161011: 16 10 13
+192: 17 8 14
+21037: 9 7 18 13
+292: 11 6 16 20
+"""
+
+def load_data(data):
+    for line in data.splitlines():
+        if line := line.strip():
+            target, remaining = line.split(': ')
+            yield int(target), tuple(map(int, remaining.split()))
+
+
+def validate(target, parts, current=None, ors=False):
+    if not parts:
+        return target == current
+    part, remaining = parts[0], parts[1:]
+
+    if current is None:
+        valid = validate(target, remaining, part, ors=ors)
+    elif current > target:
+        valid = False
+    else:
+        # Try mul first
+        valid = validate(target, remaining, current * part, ors=ors)
+        valid = valid or validate(target, remaining, current + part, ors=ors)
+        if ors:
+            valid = valid or validate(target, remaining, int(str(current)+str(part)), ors=ors)
+    return valid
+
+
+def valid_sums(data, **kwargs):
+    return sum(target for target, parts in load_data(data) if validate(target, parts, **kwargs))
+
+
+def test_a():
+    print("Testing")
+    assert valid_sums(test_data) == 3749
+    print("Tested")
+
+def test_b():
+    print("Testing")
+    assert valid_sums(test_data, ors=True) == 11387
+    print("Tested")
+
+
+
+if __name__ == '__main__':
+    test_a()
+    with open(sys.argv[1]) as f:
+        data = f.read()
+    print(f"Sum is {valid_sums(data)}")
+    test_b()
+    print(f"New Sum is {valid_sums(data, ors=True)}")
+
+