CODE 48: Maximal Rectangle

Given a 2D binary matrix filled with 0's and 1's, find the largest rectangle containing all ones and return its area.

public int maximalRectangle(char[][] matrix) {// Start typing your Java solution below// DO NOT write main() functionif (null == matrix || matrix.length <= 0) {return 0;}int rows = matrix.length;int cols = matrix[0].length;int[][] vmax = new int[rows][cols];if (matrix[0][0] == '1') {vmax[0][0] = 1;}int maximum = Integer.MIN_VALUE;for (int i = 0; i < rows; i++) {for (int j = 0; j < cols; j++) {if (i == 0) {if (matrix[i][j] == '1') {vmax[i][j] = 1;}} else {if (matrix[i][j] == '1') {vmax[i][j] = 1 + vmax[i - 1][j];} else {vmax[i][j] = 0;}}}}for (int i = rows - 1; i >= 0; i--) {int tmp = largestRectangleArea(vmax[i]);if (tmp > maximum) {maximum = tmp;}}return maximum;}