85 Maximal Rectangle

public class Solution {
    public int maximalRectangle(char[][] matrix) {
        if (matrix == null || matrix.length == 0) {
            return 0;
        }
        
        int row = matrix.length;
        int col = matrix[0].length;
        int[][] rectangle = new int[row][col];
        
        for (int i = 0; i < row; i++) {
            for (int j = 0; j < col; j++) {
                if (i == 0) {
                    rectangle[i][j] = matrix[i][j] == ‘0‘ ? 0 : 1;
                } else {
                    rectangle[i][j] = matrix[i][j] == ‘0‘ ? 0 : 1+rectangle[i - 1][j];
                }
            }
        }
        int maxArea = 0;
        for (int i = 0; i < row; i++) {
            int tem = largestRectangleArea(rectangle[i]); 
            maxArea = Math.max(tem, maxArea);
        }
        return maxArea;
    }
    public int largestRectangleArea(int[] height)  {
        int i = 0;
        int maxArea = 0;
        int[] h = new int[height.length + 1];
        h = Arrays.copyOf(height, height.length + 1);
        Stack<Integer> stack = new Stack<Integer>();
        
        while (i < h.length) {
            if (stack.isEmpty() || h[stack.peek()] <= h[i]) {
                stack.push(i++);
            } else {
                int t = stack.pop();
                maxArea = Math.max(maxArea, h[t]*(stack.isEmpty() ? i : i - stack.peek() - 1));
            }
        }
        return maxArea;
    }
    
}