Revert last commit

eval() is slow and not safe to use against not previously checked input.

day-18/day-18.py

@@ -2,6 +2,25 @@
 from pathlib import Path
 
 
+def parse(line):
+    if ',' not in line:
+        return int(line)
+    line = line[1:-1]
+    level = 0
+    split_idx = 0
+    for i, c in enumerate(line):
+        if '[' == c:
+            level += 1
+        elif ']' == c:
+            level -= 1
+        elif 0 == level and ',' == c:
+            split_idx = i
+            break
+    left = parse(line[:split_idx])
+    right = parse(line[split_idx + 1:])
+    return (left, right)
+
+
 def explode_to_left(n, l):
     (left, right) = n
     res = True
@@ -104,11 +123,10 @@ def part_1(input):
     n = None
     for line in input:
         line = line.rstrip()
-        nn = eval(line.replace('[', '(').replace(']', ')'))
         if not n:
-            n = nn
+            n = parse(line)
             continue
-        n = (n, nn)
+        n = (n, parse(line))
         res = True
         while res:
             while res:
@@ -122,7 +140,8 @@ def part_2(input):
     result = 0
     nbrs = set()
     for line in input:
-        nbrs.add(eval(line.rstrip().replace('[', '(').replace(']', ')')))
+        line = line.rstrip()
+        nbrs.add(parse(line))
     for n1 in nbrs:
         for n2 in nbrs:
             if n1 == n2: