public class Solution {    public int maximalRectangle(char[][] matrix) {        if (matrix==null||matrix.length==0||matrix[0].length==0)            return 0;        int cLen = matrix[0].length;    // column length        int rLen = matrix.length;       // row length        // height array         int[] h = new int[cLen+1];        h[cLen]=0;        int max = 0;        for (int row=0;row<rLen;row++) {            Stack<Integer> s = new Stack<Integer>();            for (int i=0;i<cLen+1;i++) {                if (i<cLen)                    if(matrix[row][i]==‘1‘)                        h[i]+=1;                    else h[i]=0;                if (s.isEmpty()||h[s.peek()]<=h[i])                    s.push(i);                else {                    while(!s.isEmpty()&&h[i]<h[s.peek()]){                        int top = s.pop();                        int area = h[top]*(s.isEmpty()?i:(i-s.peek()-1));                        if (area>max)                            max = area;                    }                    s.push(i);                }            }        }        return max;    }}