2020 day 10

2020/10/part1.js

@@ -0,0 +1,18 @@
+const fs = require('fs');
+const data = fs.readFileSync('input.txt', 'utf-8');
+const lines = data.split('\n').map(num => parseInt(num)).sort((a,b)=>(a-b));
+lines.unshift(0); // add the outlet with joltage 0
+lines.push(lines[lines.length-1]+3); // your device has a joltage 3 above the highest
+let threes = 0; // keep track of differences for puzzle solution
+let ones = 0;
+for (let i = 1; i < lines.length; i++) {
+  switch (lines[i]-lines[i-1]) {
+    case 3:
+      threes++;
+      break;
+    case 1:
+      ones++;
+      break;
+  }
+}
+console.log(ones * threes)