Add 2017/25

Author: FabijanC

year2017/day25/input.txt

@@ -0,0 +1,62 @@
+Begin in state A.
+Perform a diagnostic checksum after 12656374 steps.
+
+In state A:
+  If the current value is 0:
+    - Write the value 1.
+    - Move one slot to the right.
+    - Continue with state B.
+  If the current value is 1:
+    - Write the value 0.
+    - Move one slot to the left.
+    - Continue with state C.
+
+In state B:
+  If the current value is 0:
+    - Write the value 1.
+    - Move one slot to the left.
+    - Continue with state A.
+  If the current value is 1:
+    - Write the value 1.
+    - Move one slot to the left.
+    - Continue with state D.
+
+In state C:
+  If the current value is 0:
+    - Write the value 1.
+    - Move one slot to the right.
+    - Continue with state D.
+  If the current value is 1:
+    - Write the value 0.
+    - Move one slot to the right.
+    - Continue with state C.
+
+In state D:
+  If the current value is 0:
+    - Write the value 0.
+    - Move one slot to the left.
+    - Continue with state B.
+  If the current value is 1:
+    - Write the value 0.
+    - Move one slot to the right.
+    - Continue with state E.
+
+In state E:
+  If the current value is 0:
+    - Write the value 1.
+    - Move one slot to the right.
+    - Continue with state C.
+  If the current value is 1:
+    - Write the value 1.
+    - Move one slot to the left.
+    - Continue with state F.
+
+In state F:
+  If the current value is 0:
+    - Write the value 1.
+    - Move one slot to the left.
+    - Continue with state E.
+  If the current value is 1:
+    - Write the value 1.
+    - Move one slot to the right.
+    - Continue with state A.

year2017/day25/part1.awk

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+#!/usr/bin/awk -f
+
+function extract_word(input, i, words) {
+    patsplit(input, words, /[A-Za-z0-9]+/);
+    return words[i];
+}
+
+function direction_to_index_delta(direction) {
+    if (direction == "right") return 1;
+    if (direction == "left") return -1;
+
+    print "Error: invalid direction", direction;
+    exit 1;
+}
+
+BEGIN{RS="\n\n"}
+
+/^In state/ {
+    split($0, rows, "\n");
+
+    in_state = extract_word(rows[1], 3);
+
+    next_value_map[in_state, 0] = extract_word(rows[3], 4);
+    next_index_delta_map[in_state, 0] = direction_to_index_delta(extract_word(rows[4], 6));
+    next_state_map[in_state, 0] = extract_word(rows[5], 4);
+
+    next_value_map[in_state, 1] = extract_word(rows[7], 4);
+    next_index_delta_map[in_state, 1] = direction_to_index_delta(extract_word(rows[8], 6));
+    next_state_map[in_state, 1] = extract_word(rows[9], 4);
+
+    next;
+}
+
+/^Begin in state/{
+    split($0, rows, "\n");
+    current_state = extract_word(rows[1], 4);
+
+    total_steps = extract_word(rows[2], 6);
+}
+
+END{
+    current_index = 0;
+
+    while (total_steps--) {
+        current_value = tape[current_index] || 0;
+        next_state = next_state_map[current_state, current_value];
+        next_value = next_value_map[current_state, current_value];
+        next_index_delta = next_index_delta_map[current_state, current_value];
+
+        tape[current_index] = next_value;
+        current_state = next_state;
+        current_index += next_index_delta;
+    }
+
+    diagnostic_checksum = 0;
+    for (i in tape) {
+        diagnostic_checksum += tape[i];
+    }
+    print diagnostic_checksum;
+}

year2017/day25/sample.txt

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+Begin in state A.
+Perform a diagnostic checksum after 6 steps.
+
+In state A:
+  If the current value is 0:
+    - Write the value 1.
+    - Move one slot to the right.
+    - Continue with state B.
+  If the current value is 1:
+    - Write the value 0.
+    - Move one slot to the left.
+    - Continue with state B.
+
+In state B:
+  If the current value is 0:
+    - Write the value 1.
+    - Move one slot to the left.
+    - Continue with state A.
+  If the current value is 1:
+    - Write the value 1.
+    - Move one slot to the right.
+    - Continue with state A.