advent-of-code

commit 247b36212dd6ce2855956d336deedbf0dbd53917
parent 86c5dfa4409581e348bb8027037abdd7ccba9435
Author: finwo <finwo@pm.me>
Date:   Wed, 24 Dec 2025 16:10:54 +0100

Completed 2025/03

Diffstat:
A
2025/03/example.txt
 | 
4
++++
A
2025/03/index.js
 | 
76
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

2 files changed, 80 insertions(+), 0 deletions(-)
diff --git a/2025/03/example.txt b/2025/03/example.txt
@@ -0,0 +1,4 @@
+987654321111111
+811111111111119
+234234234234278
+818181911112111
diff --git a/2025/03/index.js b/2025/03/index.js
@@ -0,0 +1,76 @@
+#!/usr/bin/env node
+
+const fs = require('node:fs');
+
+const banks = fs
+  .readFileSync('input', 'utf-8')
+  .split('\r\n').join('\n')
+  .split('\r').join('\n')
+  .split('\n')
+  .map(str => str.trim())
+  .filter(str => str)
+  .map(bank => ({
+    batteries: bank,
+  }))
+  ;
+
+// Part 1
+for(const bank of banks) {
+  // Find the tens
+  let highestTensVal = -1;
+  let highestTensIdx = -1;
+  for(const rating of ['9','8','7','6','5','4','3','2','1']) {
+    const found = bank.batteries.indexOf(rating);
+    if (found < 0) continue;
+    if (found == (bank.batteries.length-1)) continue;
+    highestTensVal = rating;
+    highestTensIdx = found;
+    break;
+  }
+  // Find the ones
+  let highestOnesVal = -1;
+  let highestOnesIdx = -1;
+
+  for(const rating of ['9','8','7','6','5','4','3','2','1']) {
+    const found = bank.batteries.indexOf(rating, highestTensIdx+1);
+    if (found < 0) continue;
+    highestOnesVal = rating;
+    highestOnesIdx = found;
+    break;
+  }
+
+  // Save it for the records
+  bank.joltage2 = parseInt(`${highestTensVal}${highestOnesVal}`, 10);
+}
+
+// Part 2
+for(const bank of banks) {
+
+  let construct = [];
+  let currentIdx = -1;
+  while(construct.length < 12) {
+    let found = -1;
+    for(const rating of ['9','8','7','6','5','4','3','2','1']) {
+      found = bank.batteries.indexOf(rating, currentIdx + 1);
+      if (found < 0) continue;
+      if (found >= (bank.batteries.length + construct.length - 11)) {
+        found = -1;
+        continue;
+      };
+      currentIdx = found;
+      construct.push(rating);
+      break;
+    }
+    if (found < 0) {
+      throw new Error("Could not find highest number");
+    }
+  }
+
+  bank.joltage12 = BigInt(construct.join(''));
+}
+
+const part1 = banks.reduce((r,bank) => r+bank.joltage2, 0);
+const part2 = banks.reduce((r,bank) => r+bank.joltage12, 0n);
+
+process.stdout.write(`------[ Part 1: ${part1} ]------\n`);
+process.stdout.write(`------[ Part 2: ${part2} ]------\n`);