advent of code 2025 in ts and nix
dunkirk.sh
1const file = await Bun.file("../../shared/03/input.txt").text();
2const banks = file.split("\n");
3
4(() => {
5 let jolts = 0;
6 for (const bank of banks) {
7 const L = bank.length;
8
9 let highestPair = -1;
10 for (let j = 1; j <= L - 1; j++) {
11 let largestI = -1;
12 const jVal = Number.parseInt(bank[j] as string, 10);
13 for (let i = 0; i < j; i++) {
14 const iVal = Number.parseInt(bank[i] as string, 10);
15 if (iVal > largestI) largestI = iVal;
16 }
17
18 const pair = largestI * 10 + jVal;
19
20 if (pair > highestPair) highestPair = pair;
21 }
22
23 jolts += highestPair;
24 }
25
26 console.log("part 1:", jolts);
27})();
28
29(() => {
30 let jolts = 0n;
31 for (const bank of banks) {
32 const L = bank.length;
33 if (L === 0) continue;
34
35 const K = 12;
36 const joltNums: number[] = [];
37
38 for (let j = 0; j <= L - 1; j++) {
39 const jVal = Number.parseInt(bank[j] as string, 10);
40
41 // Remaining digits including current position
42 const remaining = L - j;
43
44 // Improve prefix: pop smaller tail digits if we can still reach K after popping
45 while (
46 joltNums.length > 0 &&
47 (joltNums[joltNums.length - 1] as number) < jVal &&
48 joltNums.length - 1 + remaining >= K
49 ) {
50 joltNums.pop();
51 }
52
53 // Take current if we still need digits
54 if (joltNums.length < K) {
55 joltNums.push(jVal);
56 }
57
58 // else skip
59 }
60
61 // Accumulate as BigInt
62 let acc = 0n;
63 for (const d of joltNums) {
64 acc = acc * 10n + BigInt(d);
65 }
66 jolts += acc;
67 }
68
69 console.log("part 2", jolts);
70})();