2022 day 5

2022/05/part2

@@ -0,0 +1,51 @@
+#!/usr/bin/env python
+
+import re
+
+crates = []
+
+def process_crates(spec):
+    for i in range(0, len(spec), 4):
+        pos = i // 4
+        if len(crates) < pos + 1:
+            crates.append([])
+
+        if spec[i] != '[':
+            continue
+
+        crates[pos].append(spec[i+1])
+
+def process_instruction(spec):
+    m = re.search('^move (\d+) from (\d+) to (\d+)$', spec)
+    count = int(m.group(1))
+    src = int(m.group(2)) - 1
+    dst = int(m.group(3)) - 1
+
+    items = []
+    for i in range(0, count):
+        items.append(crates[src].pop())
+    items.reverse()
+    crates[dst] = crates[dst] + items
+
+with open('input') as f:
+    # Read the diagram + separating line
+    for line in f:
+        if line[0] == ' ':
+            continue
+        if line == "\n":
+            break
+        process_crates(line.rstrip())
+
+    # We filled the lines upside down, so flip them
+    for pos in crates:
+        pos.reverse()
+
+    for line in f:
+        process_instruction(line.rstrip())
+
+out = ""
+for pos in crates:
+  out = out + pos[-1]
+
+print(out)
+