day nine both parts

09/code.js

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+import { readFileSync } from 'node:fs';
+
+let sampleMode = false;
+let usedArray = [];
+
+const sampleArray = readFileSync('sample.txt').toString().split("\n");
+const inputArray = readFileSync('input.txt').toString().split("\n");
+
+if (sampleMode) {
+  usedArray = sampleArray;
+} else {
+  usedArray = inputArray;
+}
+
+// Part One
+
+console.time("part1");
+
+let coordinatesArray = [];
+
+for (const element of usedArray) {
+  const coordinates = element.split(",");
+  coordinatesArray.push({ x: Number.parseInt(coordinates[0]), y: Number.parseInt(coordinates[1]) });
+}
+
+let segments = [];
+
+for (let i = 0; i < coordinatesArray.length; i++) {
+  for (let j = i + 1; j < coordinatesArray.length; j++) {
+    const dx = Math.abs(coordinatesArray[i].x - coordinatesArray[j].x) + 1;
+    const dy = Math.abs(coordinatesArray[i].y - coordinatesArray[j].y) + 1;
+    const area = dx * dy;
+    segments.push({ dx: dx, dy: dy, area: area });
+  }
+}
+
+segments.sort((a, b) => a.area > b.area ? -1 : 1);
+
+console.timeEnd("part1");
+console.log(segments[0].area);
+
+
+// Part Two
+
+console.time("part2");
+
+// Only collect the RED tile coordinates (endpoints)
+const xSet = new Set();
+const ySet = new Set();
+
+for (const tile of coordinatesArray) {
+  xSet.add(tile.x);
+  ySet.add(tile.y);
+}
+
+const xCoords = [...xSet].sort((a, b) => a - b);
+const yCoords = [...ySet].sort((a, b) => a - b);
+
+// Store horizontal and vertical line segments for boundary checking
+const hLines = []; // {y, x1, x2}
+const vLines = []; // {x, y1, y2}
+
+for (let i = 0; i < coordinatesArray.length; i++) {
+  const curr = coordinatesArray[i];
+  const next = coordinatesArray[(i + 1) % coordinatesArray.length];
+
+  if (curr.x === next.x) {
+    vLines.push({ x: curr.x, y1: Math.min(curr.y, next.y), y2: Math.max(curr.y, next.y) });
+  } else {
+    hLines.push({ y: curr.y, x1: Math.min(curr.x, next.x), x2: Math.max(curr.x, next.x) });
+  }
+}
+
+// Check if a point is on the boundary
+function isOnBoundary(x, y) {
+  for (const line of hLines) {
+    if (y === line.y && x >= line.x1 && x <= line.x2) return true;
+  }
+  for (const line of vLines) {
+    if (x === line.x && y >= line.y1 && y <= line.y2) return true;
+  }
+  return false;
+}
+
+// Check if a point is inside using ray casting (count vertical line crossings to the left)
+function isInside(x, y) {
+  let crossings = 0;
+  for (const line of vLines) {
+    if (line.x < x && y >= line.y1 && y < line.y2) {
+      crossings++;
+    }
+  }
+  return crossings % 2 === 1;
+}
+
+// Check if a point is valid (on boundary or inside)
+function isValid(x, y) {
+  return isOnBoundary(x, y) || isInside(x, y);
+}
+
+// Check if entire rectangle is valid
+function isRectValid(x1, y1, x2, y2) {
+  // Check all corner and edge points at compressed coordinates within the rectangle
+  for (const y of yCoords) {
+    if (y < y1 || y > y2) continue;
+    for (const x of xCoords) {
+      if (x < x1 || x > x2) continue;
+      if (!isValid(x, y)) return false;
+    }
+  }
+
+  // Also check if any boundary line crosses through the rectangle's interior
+  // creating an "outside" region
+  for (const line of vLines) {
+    if (line.x > x1 && line.x < x2) {
+      // Vertical line inside rectangle - check if it creates a gap
+      if (line.y1 > y1 || line.y2 < y2) {
+        // Line doesn't span full height - might create invalid region
+        if (line.y1 > y1 && !isValid(line.x, y1)) return false;
+        if (line.y2 < y2 && !isValid(line.x, y2)) return false;
+      }
+    }
+  }
+
+  return true;
+}
+
+// Find largest valid rectangle with red corners
+let maxArea = 0;
+
+for (let i = 0; i < coordinatesArray.length; i++) {
+  for (let j = i + 1; j < coordinatesArray.length; j++) {
+    const r1 = coordinatesArray[i];
+    const r2 = coordinatesArray[j];
+
+    const x1 = Math.min(r1.x, r2.x);
+    const x2 = Math.max(r1.x, r2.x);
+    const y1 = Math.min(r1.y, r2.y);
+    const y2 = Math.max(r1.y, r2.y);
+
+    if (isRectValid(x1, y1, x2, y2)) {
+      const area = (x2 - x1 + 1) * (y2 - y1 + 1);
+      if (area > maxArea) maxArea = area;
+    }
+  }
+}
+
+console.timeEnd("part2");
+console.log(maxArea);
+
+// functions