feat: Day 3: No Matter How You Slice It (part 2)

Author: mariotacke

day-03-no-matter-how-you-slice-it/README.md

@@ -50,5 +50,13 @@ The four square inches marked with `X` are claimed by **both `1` and `2`**. (Cla
 
 If the Elves all proceed with their own plans, none of them will have enough fabric. **How many square inches of fabric are within two or more claims?**
 
+## Part Two
+
+Amidst the chaos, you notice that exactly one claim doesn't overlap by even a single square inch of fabric with any other claim. If you can somehow draw attention to it, maybe the Elves will be able to make Santa's suit after all!
+
+For example, in the claims above, only claim `3` is intact after all claims are made.
+
+**What is the ID of the only claim that doesn't overlap?**
+
 ## References
 - https://adventofcode.com/2018/day/3

day-03-no-matter-how-you-slice-it/fabric2.js

@@ -0,0 +1,57 @@
+class Sheet {
+  constructor (width = 1000, height = 1000) {
+    this._grid = Array
+      .from({ length: height })
+      .map(() => Array
+        .from({ length: width })
+        .map(() => 0));
+  }
+
+  reserve (claim) {
+    for (let y = 0; y < claim.height; y++) {
+      for (let x = 0; x < claim.width; x++) {
+        this._grid[y + claim.top][x + claim.left] += 1;
+      }
+    }
+  }
+
+  hasOverlap (claim) {
+    const content = [];
+
+    for (let y = 0; y < claim.height; y++) {
+      for (let x = 0; x < claim.width; x++) {
+        content.push(this._grid[y + claim.top][x + claim.left]);
+      }
+    }
+
+    return content.every((x) => x === 1);
+  }
+}
+
+const fabric = (input, width = 1000, height = 1000) => {
+  const sheet = new Sheet(width, height);
+
+  const claims = input
+    .split('\n')
+    .map((x) => {
+      const parts = x.match(/#(\d+) @ (\d+),(\d+): (\d+)x(\d+)/);
+
+      return {
+        id: +parts[1],
+        top: +parts[3],
+        left: +parts[2],
+        width: +parts[4],
+        height: +parts[5],
+      };
+    });
+
+  claims.forEach((claim) => sheet.reserve(claim));
+
+  for (let i = 0; i < claims.length; i++) {
+    if (sheet.hasOverlap(claims[i])) {
+      return claims[i].id;
+    }
+  }
+};
+
+module.exports = fabric;

day-03-no-matter-how-you-slice-it/test.js

@@ -1,6 +1,7 @@
 const assert = require('assert');
 
 const fabric = require('./fabric');
+const fabric2 = require('./fabric2');
 
 describe('Day 3: No Matter How You Slice It', () => {
   it('should calculate overlapping area', () => {
@@ -11,4 +12,15 @@ describe('Day 3: No Matter How You Slice It', () => {
 
     assert.strictEqual(fabric(claims, 11, 9), 4);
   });
+
+  describe('Part Two', () => {
+    it('should determine id of lone claim', () => {
+      const claims =
+        `#1 @ 1,3: 4x4
+         #2 @ 3,1: 4x4
+         #3 @ 5,5: 2x2`;
+
+      assert.strictEqual(fabric2(claims, 11, 9), 3);
+    });
+  });
 });