Maximal Rectangle

Author: gavinfish

085 Maximal Rectangle.py

@@ -0,0 +1,33 @@
+'''
+Given a 2D binary matrix filled with 0's and 1's, find the largest rectangle containing all ones and return its area.
+'''
+
+class Solution(object):
+    def maximalRectangle(self, matrix):
+        """
+        :type matrix: List[List[str]]
+        :rtype: int
+        """
+        if not matrix or not matrix[0]:
+            return 0
+        n = len(matrix[0])
+        heights = [0 for __ in range(n + 1)]
+        result = 0
+        for row in matrix:
+            for i in range(n):
+                heights[i] = heights[i] + 1 if row[i] == '1' else 0
+            stack = [-1]
+            for i in range(n + 1):
+                while heights[i] < heights[stack[-1]]:
+                    h = heights[stack.pop()]
+                    w = i - stack[-1] - 1
+                    result = max(result, h * w)
+                stack.append(i)
+        return result
+
+
+if __name__ == "__main__":
+    assert Solution().maximalRectangle([['2', '1', '0', '1', '0', '1'],
+                                        ['0', '1', '0', '0', '1', '1'],
+                                        ['1', '1', '1', '1', '0', '1'],
+                                        ['1', '1', '1', '1', '0', '1']]) == 8