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

　　

class Solution {public:    int maximalRectangle(vector
     
      
        > &matrix) {        // Start typing your C/C++ solution below        // DO NOT write int main() function         // DO NOT write int main() function        int m = matrix.size();        if(m < 1) return 0;        int n = matrix[0].size();                vector
       
         cache(m, 0);        int i,j,area, maxArea = 0,top;        stack
        
          s;                for(i = n; i>= 0; i--)        {            for(int k = 0; k< m; k++)              if(matrix[k][i] == '1')                   cache[k] ++ ;                else                    cache[k] = 0;                               for(j= 0; j< m; )            {                 if(s.empty() || cache[j] >= cache[s.top()] )                   {                        s.push(j);                        j++;                        continue;                   }else{                          top = s.top();                          s.pop();                          area = cache[top] * ( s.empty() ? j : j - s.top() -1);                          maxArea = maxArea > area ? maxArea : area ;                                   }            }                        while(!s.empty())            {                top = s.top();                s.pop();                area = cache[top] * ( s.empty() ? j : j - s.top() -1);                maxArea = maxArea > area ? maxArea : area ;            }        }                return maxArea ;            }};