Day 9

09/part1.js

@@ -0,0 +1,23 @@
+const fs = require('fs');
+const PREAMBLE_SIZE = 25;
+
+fs.readFile('input', (err, data) => {
+  if (err) throw err;
+  let input = data.toString().trim().split("\n").map((line) => Number(line) );
+
+  let buf = input.slice(0, PREAMBLE_SIZE);
+  for(pos=PREAMBLE_SIZE;pos<input.length;pos++) {
+    let next = input[pos];
+
+    let sums = new Set( );
+    buf.forEach((a) => buf.forEach((b) => { if (a != b) sums.add(a+b); }));
+
+    if (!sums.has(next)) {
+      console.log(next);
+      break;
+    }
+
+    buf = buf.slice(1, 25);
+    buf.push(next);
+  }
+});

09/part2.js

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+const fs = require('fs');
+const PREAMBLE_SIZE = 25;
+
+function breakIt(input, target) {
+  for (i=0;i<input.length;i++) {
+    for(j=i+1;j<input.length;j++) {
+      let subset = input.slice(i, j);
+      if (target == subset.reduce((a,b) => a+b)) {
+        console.log(Math.min(...subset) + Math.max(...subset))
+        return;
+      }
+    }
+  }
+}
+
+fs.readFile('input', (err, data) => {
+  if (err) throw err;
+  let input = data.toString().trim().split("\n").map((line) => Number(line) );
+
+  let buf = input.slice(0, PREAMBLE_SIZE);
+  for(pos=PREAMBLE_SIZE;pos<input.length;pos++) {
+    let next = input[pos];
+
+    let sums = new Set();
+    buf.forEach((a) => buf.forEach((b) => { if (a != b) sums.add(a+b); }));
+
+    if (!sums.has(next)) {
+      breakIt(input, next);
+      return;
+    }
+
+    buf = buf.slice(1, 25);
+    buf.push(next);
+  }
+});