Day 4

4/solution.mjs

@@ -0,0 +1,55 @@
+import { readFileSync } from 'node:fs';
+
+const input = readFileSync('input', 'utf-8');
+
+class Range {
+  constructor(start, end) {
+    this.start = start;
+    this.end = end;
+
+    if (this.start > this.end) {
+      throw new Error('Invalid range');
+    }
+  }
+
+  containsRange(range) {
+    return (
+      this.start <= range.start &&
+      this.end >= range.end
+    );
+  }
+
+  overlaps(range) {
+    return (
+      (range.start >= this.start && range.start <= this.end) ||
+      (this.start >= range.start && this.start <= range.end)
+    );
+  }
+}
+
+const pairs = input
+  .split('\n')
+  .filter(line => line)
+  .map(line => line
+    .split(',')
+    .map(range => new Range(...range
+      .split('-')
+      .map(num => parseInt(num))
+    ))
+  );
+
+const containedPairCount = pairs
+  .map(pair =>
+    pair[0].containsRange(pair[1]) ||
+    pair[1].containsRange(pair[0])
+  )
+  .reduce((total, contains) => total + Number(contains), 0);
+
+console.log(`Contained pair count: ${containedPairCount}`);
+
+const overlappingPairCount = pairs
+  .map(pair => pair[0].overlaps(pair[1]))
+  .reduce((total, overlaps) => total + Number(overlaps), 0)
+
+console.log(`Overlapping pair count: ${overlappingPairCount}`);
+