Solve 2018 day 17

2018/d17.py

@@ -0,0 +1,136 @@
+from lib import get_data, str_to_ints, add2
+
+
+def above(p):
+    return add2(p, (0, -1))
+
+
+def below(p):
+    return add2(p, (0, 1))
+
+
+def right(p):
+    return add2(p, (1, 0))
+
+
+def left(p):
+    return add2(p, (-1, 0))
+
+
+def print2d(xs, ys=[], zs=[], cs=".#~|"):
+    xs, ys, zs = set(xs), set(ys), set(zs)
+    all = xs | ys | zs
+    x_min, x_max, y_min, y_max = 10**9, 0, 10**9, 0
+    for x, y in all:
+        x_min = min(x_min, x)
+        y_min = min(y_min, y)
+        x_max = max(x_max, x)
+        y_max = max(y_max, y)
+    for y in range(y_min, y_max + 1):
+        row = ""
+        for x in range(x_min, x_max + 1):
+            if (x, y) in xs:
+                row += cs[1]
+            elif (x, y) in ys:
+                row += cs[2]
+            elif (x, y) in zs:
+                row += cs[3]
+            else:
+                row += cs[0]
+        print(row)
+
+
+def part_1(data):
+    sand = []
+    max_y = 0
+    min_y = 10**9
+    for line in data.splitlines():
+        line = line.strip()
+        a, b, c = str_to_ints(line)
+        if line.startswith("x"):
+            x = a
+            for y in range(b, c + 1):
+                max_y = max(max_y, y)
+                min_y = min(min_y, y)
+                sand.append((x, y))
+        elif line.startswith("y"):
+            y = a
+            max_y = max(max_y, y)
+            min_y = min(min_y, y)
+            for x in range(b, c + 1):
+                sand.append((x, y))
+        else:
+            assert False
+
+    # TODO: probably should use 2D array for better perf
+    sources = [(500, 0)]
+    water = set()
+    sand = set(sand)
+    water_rest = set()
+
+    while sources:
+        source = sources.pop()
+        current = below(source)
+        while current[1] <= max_y:
+            if current[1] < min_y:
+                current = below(current)
+            elif current in water_rest:
+                break
+            elif below(current) in sand or below(current) in water_rest:
+                water.add(current)
+                c = current
+                to_water_rest = [current]
+                left_sand, right_sand = False, False
+                while True:
+                    c = right(c)
+                    if c in sand:
+                        right_sand = True
+                        break
+                    elif below(c) in sand or below(c) in water_rest:
+                        water.add(c)
+                        to_water_rest.append(c)
+                    else:
+                        # it's empty underneath
+                        water.add(c)
+                        sources.append(c)
+                        break
+
+                c = current
+                while True:
+                    c = left(c)
+                    if c in sand:
+                        left_sand = True
+                        break
+                    elif below(c) in sand or below(c) in water_rest:
+                        water.add(c)
+                        to_water_rest.append(c)
+                    else:
+                        # it's empty underneath
+                        water.add(c)
+                        sources.append(c)
+                        break
+
+                if left_sand and right_sand:
+                    sources.append(above(above(current)))
+                    for w in to_water_rest:
+                        water_rest.add(w)
+                break
+            else:
+                water.add(current)
+                current = below(current)
+
+        # print2d(sand, water_rest, water)
+        # print(sources)
+        # input()
+    current_water = len(water_rest | water)
+    print(current_water)
+    print(len(water_rest))
+
+
+def main():
+    data = get_data(__file__)
+    part_1(data)
+
+
+if __name__ == "__main__":
+    main()

README.md

@@ -105,7 +105,8 @@ written in Python.
 - Day 14: 20:48
 - Day 15: 185:11
 - Day 16: 36:10
-
+- Day 17: 180:00
+- Day 18:
 
 # 2022