Day 20

20/solution.mjs

@@ -0,0 +1,55 @@
+import { readFileSync } from 'node:fs';
+
+const input = readFileSync('input', 'utf-8');
+
+const numbers = input
+  .split('\n')
+  .filter(line => !!line.trim())
+  .map(num => parseInt(num));
+
+function getNextPos(pos, move, len) {
+  if (move === 0) {
+    return pos;
+  } else if (move > 0) {
+    return (pos + move) % (len - 1);
+  } else {
+    return (len - 1) - ((len - 1 - pos + Math.abs(move)) % (len - 1));
+  }
+}
+
+function mix(numberArray, count=1) {
+  const sequence = numberArray.map((move, sequence) => ({move, sequence}));
+
+  for (let c = 0; c < count; c++) {
+    for (let i = 0; i < sequence.length; i++) {
+      const itemIndex = sequence.findIndex(item => item.sequence === i);
+      const item = sequence[itemIndex];
+
+      const newIndex = getNextPos(itemIndex, item.move, sequence.length);
+
+      sequence.splice(itemIndex, 1);
+      sequence.splice(newIndex, 0, item);
+    }
+  }
+
+  return sequence.map(s => s.move);
+}
+
+function getCoordinates(mixed) {
+  const zeroIndex = mixed.indexOf(0);
+  const coordinates = (
+    mixed[(zeroIndex + 1000) % (mixed.length)] +
+    mixed[(zeroIndex + 2000) % (mixed.length)] +
+    mixed[(zeroIndex + 3000) % (mixed.length)]
+  );
+  return coordinates;
+}
+
+const partOneMixed = mix(numbers);
+const partOneCoords = getCoordinates(partOneMixed);
+console.log('The sum of grove coordinates for part one is:', partOneCoords);
+
+const partTwoNumbers = numbers.map(n => n * 811589153);
+const partTwoMixed = mix(partTwoNumbers, 10);
+const partTwoCoords = getCoordinates(partTwoMixed);
+console.log('The sum of grove coordinates for part two is:', partTwoCoords);