Solve day 13 2017.

2017/d13.py

@@ -0,0 +1,52 @@
+from lib import str_to_ints
+
+
+def part_1(data):
+    layer_to_depth = {}
+    for line in data.splitlines():
+        a, b = str_to_ints(line)
+        layer_to_depth[a] = b
+
+    layer_to_pos = {l: 0 for l in layer_to_depth.keys()}
+    layer_to_dir = {l: -1 for l in layer_to_depth.keys()}
+    target = max(list(layer_to_depth.keys()))
+
+    r = 0
+    layer = 0
+    while layer <= target:
+        if layer in layer_to_pos and layer_to_pos[layer] == 0:
+            r += (layer * layer_to_depth[layer])
+
+        for k in layer_to_pos.keys():
+            if layer_to_pos[k] == 0 or (layer_to_pos[k] + 1) == layer_to_depth[k]:
+                layer_to_dir[k] *= -1
+            layer_to_pos[k] += layer_to_dir[k]
+        layer += 1
+    print(r)
+
+
+def part_2(data):
+    eqs = []
+    for line in data.splitlines():
+        layer, depth = str_to_ints(line)
+        period = (depth - 1) * 2
+        eqs.append((layer, period))
+        
+    for delay in range(1, 1_000_000_000):
+        for layer, period in eqs:
+            if (delay + layer) % period == 0:
+                break
+        else:
+            print(delay)
+            return
+
+
+
+def main():
+    data = open(0).read().strip()
+    part_1(data)
+    part_2(data)
+
+
+if __name__ == "__main__":
+    main()

README.md

@@ -73,4 +73,5 @@ written in Python.
 - Day 10: 55:00
 - Day 11: 66:06
 - Day 12: 6:44
-- Day 13:
+- Day 13: 120:00
+- Day 14: