2021 Day 14

2021-12-14 12:16:02 +01:00 · 2021-12-14 12:16:02 +01:00 · 5929e63062
commit 5929e63062
parent e2466aa44a
7 changed files with 274 additions and 1 deletions
--- a/2021/14/README.md
+++ b/2021/14/README.md
@ -0,0 +1,68 @@
+# 2021 Day 14: Extended Polymerization
+Copyright (c) Eric Wastl
+#### [Direct Link](https://adventofcode.com/2021/day/14)
+
+## Part 1
+
+The incredible pressures at this depth are starting to put a strain on your submarine. The submarine has [polymerization](https://en.wikipedia.org/wiki/Polymerization) equipment that would produce suitable materials to reinforce the submarine, and the nearby volcanically-active caves should even have the necessary input elements in sufficient quantities.
+
+The submarine manual contains instructions for finding the optimal polymer formula; specifically, it offers a **polymer template** and a list of **pair insertion** rules (your puzzle input). You just need to work out what polymer would result after repeating the pair insertion process a few times.
+
+For example:
+
+```
+NNCB
+
+CH -> B
+HH -> N
+CB -> H
+NH -> C
+HB -> C
+HC -> B
+HN -> C
+NN -> C
+BH -> H
+NC -> B
+NB -> B
+BN -> B
+BB -> N
+BC -> B
+CC -> N
+CN -> C
+```
+
+The first line is the **polymer template** - this is the starting point of the process.
+
+The following section defines the **pair insertion** rules. A rule like `AB -> C` means that when elements `A` and `B` are immediately adjacent, element `C` should be inserted between them. These insertions all happen simultaneously.
+
+So, starting with the polymer template `NNCB`, the first step simultaneously considers all three pairs:
+
+- The first pair (`NN`) matches the rule `NN` -> `C`, so element `C` is inserted between the first `N` and the second `N`.
+- The second pair (`NC`) matches the rule `NC` -> `B`, so element `B` is inserted between the `N` and the `C`.
+- The third pair (`CB`) matches the rule `CB -> H`, so element `H is inserted between the `C` and the `B`.
+
+Note that these pairs overlap: the second element of one pair is the first element of the next pair. Also, because all pairs are considered simultaneously, inserted elements are not considered to be part of a pair until the next step.
+
+After the first step of this process, the polymer becomes `NCNBCHB`.
+
+Here are the results of a few steps using the above rules:
+
+```
+Template:     NNCB
+After step 1: NCNBCHB
+After step 2: NBCCNBBBCBHCB
+After step 3: NBBBCNCCNBBNBNBBCHBHHBCHB
+After step 4: NBBNBNBBCCNBCNCCNBBNBBNBBBNBBNBBCBHCBHHNHCBBCBHCB
+```
+
+This polymer grows quickly. After step 5, it has length 97; After step 10, it has length 3073. After step 10, `B` occurs 1749 times, `C` occurs 298 times, `H` occurs 161 times, and `N` occurs 865 times; taking the quantity of the most common element (B, 1749) and subtracting the quantity of the least common element (`H`, 161) produces `1749 - 161 = 1588`.
+
+Apply 10 steps of pair insertion to the polymer template and find the most and least common elements in the result. **What do you get if you take the quantity of the most common element and subtract the quantity of the least common element?**
+
+## Part 2
+
+The resulting polymer isn't nearly strong enough to reinforce the submarine. You'll need to run more steps of the pair insertion process; a total of **40 steps** should do it.
+
+In the above example, the most common element is `B` (occurring `2192039569602` times) and the least common element is `H` (occurring `3849876073` times); subtracting these produces **`2188189693529`**.
+
+Apply **40** steps of pair insertion to the polymer template and find the most and least common elements in the result. **What do you get if you take the quantity of the most common element and subtract the quantity of the least common element?**
--- a/2021/14/code.py
+++ b/2021/14/code.py
@ -0,0 +1,48 @@
+# SPDX-License-Identifier: MIT
+# Copyright (c) 2021 Akumatic
+#
+# https://adventofcode.com/2021/day/14
+
+def read_file(filename: str = "input.txt") -> tuple:
+    with open(f"{__file__.rstrip('code.py')}{filename}", "r") as f:
+        lines = [line for line in f.read().strip().split("\n")]
+    template = lines[0]
+    rules = {x[0]: x[1] for x in (line.split(" -> ") for line in lines[2:])}
+    return template, rules
+
+def add_to_dict(d: dict, key: str, val: int = 1):
+    if key not in d:
+        d[key] = val
+    else:
+        d[key] += val
+
+def count(polymer: str, rules: dict, iterations: int) -> dict:
+    pairs = dict()
+    for i in range(len(polymer) - 1):
+        add_to_dict(pairs, polymer[i] + polymer[i+1])
+
+    for _ in range(iterations):
+        tmp = dict()
+        for pair in pairs:
+            add_to_dict(tmp, pair[0] + rules[pair], pairs[pair])
+            add_to_dict(tmp, rules[pair] + pair[1], pairs[pair])
+        pairs = tmp
+
+    elements = dict()
+    for pair in pairs:
+        add_to_dict(elements, pair[0], pairs[pair])
+    add_to_dict(elements, polymer[-1])
+    return elements
+
+def part1(template: str, insertion_rules: dict) -> int:
+    letters = count(template, insertion_rules, 10)
+    return max(letters.values()) - min(letters.values())
+
+def part2(template: str, insertion_rules: dict) -> int:
+    letters = count(template, insertion_rules, 40)
+    return max(letters.values()) - min(letters.values())
+    
+if __name__ == "__main__":
+    vals = read_file() # vals[0] is the template, vals[1] the insertion rules
+    print(f"Part 1: {part1(*vals)}")
+    print(f"Part 2: {part2(*vals)}")
--- a/2021/14/input.txt
+++ b/2021/14/input.txt
@ -0,0 +1,102 @@
+HBCHSNFFVOBNOFHFOBNO
+
+HF -> O
+KF -> F
+NK -> F
+BN -> O
+OH -> H
+VC -> F
+PK -> B
+SO -> B
+PP -> H
+KO -> F
+VN -> S
+OS -> B
+NP -> C
+OV -> C
+CS -> P
+BH -> P
+SS -> P
+BB -> H
+PH -> V
+HN -> F
+KV -> H
+HC -> B
+BC -> P
+CK -> P
+PS -> O
+SH -> N
+FH -> N
+NN -> P
+HS -> O
+CB -> F
+HH -> F
+SB -> P
+NB -> F
+BO -> V
+PN -> H
+VP -> B
+SC -> C
+HB -> H
+FP -> O
+FC -> H
+KP -> B
+FB -> B
+VK -> F
+CV -> P
+VF -> V
+SP -> K
+CC -> K
+HV -> P
+NC -> N
+VH -> K
+PF -> P
+PB -> S
+BF -> K
+FF -> C
+FV -> V
+KS -> H
+VB -> F
+SV -> F
+HO -> B
+FN -> C
+SN -> F
+OB -> N
+KN -> P
+BV -> H
+ON -> N
+NF -> S
+OF -> P
+NV -> S
+VS -> C
+OO -> C
+BP -> H
+BK -> N
+CP -> N
+PC -> K
+CN -> H
+KB -> B
+BS -> P
+KK -> P
+SF -> V
+CO -> V
+CH -> P
+FO -> B
+FS -> F
+VO -> H
+NS -> F
+KC -> H
+VV -> K
+NO -> P
+OK -> F
+PO -> V
+FK -> H
+OP -> H
+PV -> N
+CF -> P
+NH -> K
+SK -> O
+KH -> P
+HP -> V
+OC -> V
+HK -> F
--- a/2021/14/solution.txt
+++ b/2021/14/solution.txt
@ -0,0 +1,2 @@
+Part 1: 3408
+Part 2: 3724343376942
--- a/2021/14/test_code.py
+++ b/2021/14/test_code.py
@ -0,0 +1,35 @@
+# SPDX-License-Identifier: MIT
+# Copyright (c) 2021 Akumatic
+
+from code import part1, part2, read_file, count
+
+def count_chars(s: str) -> dict:
+    cnt = dict()
+    for c in s:
+        if c in cnt:
+            cnt[c] += 1
+        else:
+            cnt[c] = 1
+    return cnt
+
+def test():
+    vals = read_file("test_input.txt")
+    assert count(vals[0], vals[1], 1) == count_chars("NCNBCHB")
+    assert count(vals[0], vals[1], 2) == count_chars("NBCCNBBBCBHCB")
+    assert count(vals[0], vals[1], 3) == count_chars("NBBBCNCCNBBNBNBBCHBHHBCHB")
+    assert count(vals[0], vals[1], 4) == count_chars("NBBNBNBBCCNBCNCCNBBNBBNBBBNBBNBBCBHCBHHNHCBBCBHCB")
+    print("Passed Counting")
+
+    elements = count(vals[0], vals[1], 10)
+    assert elements == {"B": 1749, "C": 298, "H": 161, "N": 865}
+    assert part1(*vals) == 1588
+    print("Passed Part 1")
+    
+    elements = count(vals[0], vals[1], 40)
+    assert elements["B"] == 2192039569602
+    assert elements["H"] == 3849876073
+    assert part2(*vals) == 2188189693529
+    print("Passed Part 2")
+
+if __name__ == "__main__":
+    test()
--- a/2021/14/test_input.txt
+++ b/2021/14/test_input.txt
@ -0,0 +1,18 @@
+NNCB
+
+CH -> B
+HH -> N
+CB -> H
+NH -> C
+HB -> C
+HC -> B
+HN -> C
+NN -> C
+BH -> H
+NC -> B
+NB -> B
+BN -> B
+BB -> N
+BC -> B
+CC -> N
+CN -> C
--- a/2021/README.md
+++ b/2021/README.md
@ -28,7 +28,7 @@ Collect stars by solving puzzles. Two puzzles will be made available on each day
 | 11 | :white_check_mark: | :white_check_mark: | [Solution](11/code.py) | [Day 11](https://adventofcode.com/2021/day/11) |
 | 12 | :white_check_mark: | :white_check_mark: | [Solution](12/code.py) | [Day 12](https://adventofcode.com/2021/day/12) |
 | 13 | :white_check_mark: | :white_check_mark: | [Solution](13/code.py) | [Day 13](https://adventofcode.com/2021/day/13) |
-| 14 |  |  |  |  |
+| 14 | :white_check_mark: | :white_check_mark: | [Solution](14/code.py) | [Day 14](https://adventofcode.com/2021/day/14) |
 | 15 |  |  |  |  |
 | 16 |  |  |  |  |
 | 17 |  |  |  |  |