added Maximal_square.js file

Author: kav1239

Maximal_square.js

@@ -0,0 +1,53 @@
+/*
+Maximal Area of Square
+
+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.
+
+Example 1 Input: matrix = [["1","0","1","0","0"],["1","0","1","1","1"],["1","1","1","1","1"],["1","0","0","1","0"]]
+Output: 4
+
+
+Example 2 Input: matrix = [["0","1"],["1","0"]]
+Output: 1
+
+
+Example 3 Input: matrix = [["0"]]
+Output: 0
+
+
+*/
+
+/**
+ * @param {character[][]} matrix
+ * @return {number}
+ */
+var maximalSquare = function(matrix) {
+    var m = matrix.length;
+  var n = (matrix[0] || []).length;
+  var dp = Array(m).fill(0).map(_ => Array(n));
+  var max = 0;
+
+  for (var k = 0; k < m; k++) {
+    dp[k][0] = matrix[k][0] === '1' ? 1 : 0;
+    max = Math.max(max, dp[k][0]);
+  }
+
+  for (var p = 0; p < n; p++) {
+    dp[0][p] = matrix[0][p] === '1' ? 1 : 0;
+    max = Math.max(max, dp[0][p]);
+  }
+
+  for (var i = 1; i < m; i++) {
+    for (var j = 1; j < n; j++) {
+      if (matrix[i][j] === '1') {
+        dp[i][j] = Math.min(dp[i - 1][j - 1], dp[i - 1][j], dp[i][j - 1]) + 1;
+        max = Math.max(max, dp[i][j]);
+      } else {
+        dp[i][j] = 0;
+      }
+    }
+  }
+
+  return max * max;
+    
+};