int maximalRectangle(vector<vector<char>>& matrix) {

if (matrix.empty()) return 0;

vector<int> hists;

hists.resize(matrix[0].size());

int max_area = 0;

for (int i = 0; i < matrix.size(); i++)

{

for (int j = 0; j < matrix[0].size(); j++)

{

hists[j] = matrix[i][j] == '0' ? 0 : (1 + hists[j]);

}

max_area = max(max_area, largestRectangleArea(hists));

}

return max_area;

}

int largestRectangleArea(vector<int>& heights) {

stack<int> stk;

int max_area = 0;

int i = 0;

vector<int> h = heights;

h.push_back(0);

while (i < h.size())

{

if (stk.empty() || h[stk.top()] <= h[i])

{

stk.push(i++);

}

else

{

int j = stk.top();

stk.pop();

max_area = max(max_area, h[j] * (stk.empty() ? i : i - stk.top() - 1));

}

}

return max_area;

}