Add solution #221

Author: JoshCrozier

README.md

@@ -202,6 +202,7 @@
 218|[The Skyline Problem](./0218-the-skyline-problem.js)|Hard|
 219|[Contains Duplicate II](./0219-contains-duplicate-ii.js)|Easy|
 220|[Contains Duplicate III](./0220-contains-duplicate-iii.js)|Hard|
+221|[Maximal Square](./0221-maximal-square.js)|Medium|
 222|[Count Complete Tree Nodes](./0222-count-complete-tree-nodes.js)|Easy|
 224|[Basic Calculator](./0224-basic-calculator.js)|Hard|
 225|[Implement Stack using Queues](./0225-implement-stack-using-queues.js)|Easy|

solutions/0221-maximal-square.js

@@ -0,0 +1,27 @@
+/**
+ * 221. Maximal Square
+ * https://leetcode.com/problems/maximal-square/
+ * Difficulty: Medium
+ *
+ * Given an m x n binary matrix filled with 0's and 1's, find the largest square containing only
+ * 1's and return its area.
+ */
+
+/**
+ * @param {character[][]} matrix
+ * @return {number}
+ */
+var maximalSquare = function(matrix) {
+  const dp = [...new Array(matrix.length + 1)].map(() => new Array(matrix[0].length + 1).fill(0));
+  let max = 0;
+
+  for (let i = 1; i < dp.length; i++) {
+    for (let j = 1; j < dp[0].length; j++) {
+      if (matrix[i - 1][j - 1] === '1') {
+        max = Math.max(max, dp[i][j] = Math.min(dp[i - 1][j], dp[i][j - 1], dp[i - 1][j - 1]) + 1);
+      }
+    }
+  }
+
+  return max ** 2;
+};