Largest Rectangle 的follow up

Problem

Given a 2D boolean matrix filled with False and True, find the largest rectangle containing all True and return its area.

Example
Given a matrix:

[
  [1, 1, 0, 0, 1],
  [0, 1, 0, 0, 1],
  [0, 0, 1, 1, 1],
  [0, 0, 1, 1, 1],
  [0, 0, 0, 0, 1]
]
return 6.

思路

• 将每一行都当作求largest rectangle

    public int maximalRectangle(boolean[][] matrix) {
        // Write your code here
        int m = matrix.length;
        int n = m == 0 ? 0 : matrix[0].length;
        int[][] height = new int[m][n + 1];

        int maxArea = 0;
        for (int i = 0; i < m; i++) {
            for (int j = 0; j < n; j++) {
                if (! matrix[i][j]) {
                    height[i][j] = 0;
                } else {
                    height[i][j] = i == 0 ? 1 : height[i - 1][j] + 1;
                }
            }
        }

        for (int i = 0; i < m; i++) {
            int area = maxAreaInHist(height[i]);
            if (area > maxArea) {
                maxArea = area;
            }
        }

        return maxArea;
    }