Finish 2017.

2017/d25.py

@@ -0,0 +1,58 @@
+from lib import str_to_int
+from collections import defaultdict
+
+
+def part_1(data):
+    rules = {}
+    steps = None
+    start_state = None
+    current_state = None
+    current_value = None
+    for line in data.splitlines():
+        if line.startswith("In state"):
+            current_state = line[-2]
+            rules[current_state] = {}
+        elif "current value" in line:
+            current_value = str_to_int(line)
+            rules[current_state][current_value] = []
+        elif "- Write the value" in line:
+            rules[current_state][current_value].append(str_to_int(line))
+        elif "- Move one slot to the right" in line:
+            rules[current_state][current_value].append(1)
+        elif "- Move one slot to the left" in line:
+            rules[current_state][current_value].append(-1)
+        elif "Continue with state" in line:
+            rules[current_state][current_value].append(line[-2])
+        elif "Begin in state" in line:
+            start_state = line[-2]
+        elif "checksum after" in line:
+            steps = str_to_int(line)
+        elif line.strip() == "":
+            pass
+        else:
+            print(line)
+            assert False
+
+    assert type(steps) is int
+    assert start_state is not None
+    current_state = start_state
+    tape = defaultdict(int)
+    pos = 0
+    for _ in range(steps):
+        current_value = tape[pos]
+        write_value, move, next_state = rules[current_state][current_value]
+        tape[pos] = write_value
+        pos += move
+        current_state = next_state
+
+    print(sum(tape.values()))
+
+
+def main():
+    with open("i25.txt") as f:
+        data = f.read()
+    part_1(data)
+
+
+if __name__ == "__main__":
+    main()