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.

　　

class Solution {
public:
    int maximalRectangle(vector<vector<char> > &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<int> cache(m, 0);
        int i,j,area, maxArea = 0,top;
        stack<int> 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 ;
        
    }
};