LeetCode-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 class Solution {
    public int maximalRectangle(char[][] matrix) {
        if (matrix == null || matrix.length <= 0 || matrix[0].length <= 0) {
            return 0;
        }
        int rows = matrix.length;
        int cols = matrix[0].length;
        int[] height = new int[cols];
        int[] left = new int[cols];
        int[] right = new int[cols];
        int max = 0;
        for (int i = 0; i < cols; i++) {
            right[i] = cols;
        }
        for (int i = 0; i < rows; i++) {
            int curLeft = 0;
            int curRight = cols;
            for (int j = 0; j < cols; j++) {
                if (matrix[i][j] == '1') {
                    height[j]++;
                    left[j] = Math.max(curLeft, left[j]);
                } else {
                    height[j] = 0;
                    curLeft = j + 1;
                    left[j] = 0;
                }
            }
 
            for (int j = cols - 1; j >= 0; j--) {
                if (matrix[i][j] == '1') {
                    right[j] = Math.min(curRight, right[j]);
                } else {
                    right[j] = cols;
                    curRight = j;
                }
                max = Math.max(max, (right[j] - left[j]) * height[j]);
            }
        }
        return max;
    }
}