Given a rows x cols binary matrix filled with 0's and 1's, find the largest rectangle 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: 6 Explanation: The maximal rectangle is shown in the above picture. Example 2: Input: matrix = [] Output: 0 Example 3: Input: matrix = [["0"]] Output: 0 Example 4: Input: matrix = [["1"]] Output: 1 Example 5: Input: matrix = [["0","0"]] Output: 0 Constraints: rows == matrix.length cols == matrix[i].length 0 <= row, cols <= 200 matrix[i][j] is '0' or '1'.