Add solution #850

Author: JoshCrozier

README.md

@@ -657,6 +657,7 @@
 847|[Shortest Path Visiting All Nodes](./0847-shortest-path-visiting-all-nodes.js)|Hard|
 848|[Shifting Letters](./0848-shifting-letters.js)|Medium|
 849|[Maximize Distance to Closest Person](./0849-maximize-distance-to-closest-person.js)|Medium|
+850|[Rectangle Area II](./0850-rectangle-area-ii.js)|Hard|
 867|[Transpose Matrix](./0867-transpose-matrix.js)|Easy|
 868|[Binary Gap](./0868-binary-gap.js)|Easy|
 872|[Leaf-Similar Trees](./0872-leaf-similar-trees.js)|Easy|

solutions/0850-rectangle-area-ii.js

@@ -0,0 +1,72 @@
+/**
+ * 850. Rectangle Area II
+ * https://leetcode.com/problems/rectangle-area-ii/
+ * Difficulty: Hard
+ *
+ * You are given a 2D array of axis-aligned rectangles. Each rectangle[i] = [xi1, yi1, xi2, yi2]
+ * denotes the ith rectangle where (xi1, yi1) are the coordinates of the bottom-left corner, and
+ * (xi2, yi2) are the coordinates of the top-right corner.
+ *
+ * Calculate the total area covered by all rectangles in the plane. Any area covered by two or more
+ * rectangles should only be counted once.
+ *
+ * Return the total area. Since the answer may be too large, return it modulo 109 + 7.
+ */
+
+/**
+ * @param {number[][]} rectangles
+ * @return {number}
+ */
+var rectangleArea = function(rectangles) {
+  const MOD = 1e9 + 7;
+  const events = [];
+  const xCoords = new Set();
+  const yCoords = new Set();
+
+  for (const [x1, y1, x2, y2] of rectangles) {
+    xCoords.add(x1);
+    xCoords.add(x2);
+    yCoords.add(y1);
+    yCoords.add(y2);
+    events.push([x1, 1, y1, y2]);
+    events.push([x2, -1, y1, y2]);
+  }
+
+  const xArray = [...xCoords].sort((a, b) => a - b);
+  const yArray = [...yCoords].sort((a, b) => a - b);
+
+  const xMap = new Map();
+  const yMap = new Map();
+
+  for (let i = 0; i < xArray.length; i++) {
+    xMap.set(xArray[i], i);
+  }
+
+  for (let i = 0; i < yArray.length; i++) {
+    yMap.set(yArray[i], i);
+  }
+
+  const grid = Array(xArray.length).fill(0).map(() => Array(yArray.length).fill(0));
+
+  for (const [x1, y1, x2, y2] of rectangles) {
+    for (let x = xMap.get(x1); x < xMap.get(x2); x++) {
+      for (let y = yMap.get(y1); y < yMap.get(y2); y++) {
+        grid[x][y] = 1;
+      }
+    }
+  }
+
+  let totalArea = 0;
+
+  for (let x = 0; x < xArray.length - 1; x++) {
+    for (let y = 0; y < yArray.length - 1; y++) {
+      if (grid[x][y]) {
+        const width = xArray[x + 1] - xArray[x];
+        const height = yArray[y + 1] - yArray[y];
+        totalArea = (totalArea + width * height) % MOD;
+      }
+    }
+  }
+
+  return totalArea;
+};