[leetcode]85. Maximal Rectangle(Java)

https://leetcode.com/problems/maximal-rectangle/#/description

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

For example, given the following matrix:

1 0 1 0 0
1 0 1 1 1
1 1 1 1 1
1 0 0 1 0

Return 6.

package go.jacob.day703;

import java.util.Stack;


public class Demo1 {
	/*
	 * 本体解法基于84. Largest Rectangle in Histogram
	 * 把每一行看成求直方图中最大矩形面积问题
	 */
	public int maximalRectangle(char[][] matrix) {
		if (matrix == null || matrix.length == 0 || matrix[0].length == 0)
			return 0;
		int m = matrix.length, n = matrix[0].length;
		int max = 0;
		int[] h = new int[n];
		for (int i = 0; i < m; i++) {
			Stack stack = new Stack();
			stack.push(-1);
			for (int j = 0; j < n; j++) {
				if (matrix[i][j] == '1')
					h[j] += 1;
				else
					h[j] = 0;

			}
			for (int j = 0; j < n; j++) {
				while (stack.peek() != -1 && h[j] < h[stack.peek()]) {
					int top = stack.pop();
					max = Math.max(max, (j - 1 - stack.peek()) * h[top]);
				}
				stack.push(j);
			}
			while (stack.peek() != -1) {
				int top = stack.pop();
				max = Math.max(max, (n - 1 - stack.peek()) * h[top]);
			}
		}
		return max;
	}

}