More efficiently scan lines

2019/aoc2019/day19.py

@@ -1,6 +1,6 @@
 import copy
 from itertools import product
-from typing import TextIO
+from typing import TextIO, Tuple
 
 from aoc2019.intcode import Computer, read_program
 
@@ -15,7 +15,31 @@ def query_position(x: int, y: int, computer: Computer) -> bool:
     return computer.get_output() == 1
 
 
+def find_line(y: int, x_min: int, x_max: int, computer: Computer) -> Tuple[int, int]:
+    # First find start of the line:
+    offset = 0
+
+    while not query_position(x_min, y, computer):
+        offset += 1
+        x_min += 1
+
+    x_max += offset
+    while query_position(x_max, y, computer):
+        x_max += 1
+
+    x_max -= 1
+
+    return x_min, x_max
+
+
 def part1(data: TextIO) -> int:
     computer = Computer(read_program(data))
 
-    return sum(1 for x, y in product(range(50), range(50)) if query_position(x, y, computer))
+    x_min, x_max = (0, 0)
+    total = 0
+
+    for y in range(50):
+        x_min, x_max = find_line(y, x_min, x_max, computer)
+        total += min(x_max, 49) - min(x_min, 50) + 1
+
+    return total