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) {
        int row = matrix.length;
		if(row == 0) return 0;
		
		int column = matrix[0].length;
		int[][] consecutiveOnes = new int[row][column];
		for(int i = 0; i < row; ++i) {
			for(int j = 0; j < column; ++j){
				if(matrix[i][j] - '0' == 1){
					if(j == 0) 
						consecutiveOnes[i][j] = 1;
					else 
						consecutiveOnes[i][j] = consecutiveOnes[i][j - 1] + 1;
				}
				else
					consecutiveOnes[i][j] = 0;
			}
		}
		
		//calculate the max area. we check each element of consecutiveOnes column by column 
		int maxArea = 0;
		for(int i = 0; i < column; ++i){
			for(int j = 0; j < row; ++j){
				if(consecutiveOnes[j][i] != 0){
					int minWidth = consecutiveOnes[j][i];
					int index = j;
					while(index >= 0 && consecutiveOnes[index][i] != 0){
						minWidth = Math.min(minWidth, consecutiveOnes[index][i]);
						maxArea = Math.max(maxArea, minWidth * (j - index + 1));
						--index;
					}
				}
			}
		}
		return maxArea;
    }
}

　　

Remark: the second part (to seek the max area) can be solved by method used in "largest rectangle histogram" problem. Therefore, there is an algorithm with time O(row * column).