Day 15

challenges/2020/15.js

@@ -0,0 +1,34 @@
+const solvePuzzle = (input, endTurn = 30000000) => {
+  input = input.split(',').map((n, i) => [Number(n), i + 1]);
+  const memo = new Map(input);
+
+  let turn = input.length;
+  let lastNum = Number(input[input.length - 1]);
+
+  while (turn < endTurn) {
+    const age = memo.get(lastNum);
+
+    memo.set(lastNum, turn);
+
+    lastNum = age ? turn - age : 0;
+
+    turn += 1;
+  }
+  return lastNum;
+};
+
+// eslint-disable-next-line no-undef
+test('Puzzle Result', (done) => {
+  const fs = require('fs');
+  const path = require('path');
+  const currentDay = path.basename(__filename).split('.')[0];
+
+  fs.readFile(`${__dirname}/inputs/${currentDay}.txt`, (err, input) => {
+    if (err) {
+      throw err;
+    }
+    const result = solvePuzzle(input.toString());
+    console.log('\x1b[1m\x1b[31m%s\x1b[0m', 'Result:', result);
+    done();
+  });
+});

challenges/2020/inputs/15.txt

@@ -0,0 +1 @@
+7,14,0,17,11,1,2