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 largestRectangleArea(int* height, int length) {
        std::stack<int> s;
        int i = 0;
        int maxArea = 0;
        while(i < length){
            if(s.empty() || height[s.top()] <= height[i]){
                s.push(i++);
            }else {
                int t = s.top();
    			s.pop();
				int area = height[t] * (s.empty() ? i : i - s.top() - 1);
                maxArea = maxArea > area ? maxArea : area;
            }
        }
        return maxArea;
    }
int maximalRectangle(std::vector<std::vector<char> > &matrix) {
        int m = matrix.size();
        if(m == 0)return 0;
		int n = matrix[0].size();
        if(n == 0)return 0;
		int** dp = new int*[m];
		for(int i = 0; i < m; ++i){
			dp[i] = new int[n+1];
			memset(dp[i], 0, sizeof(int)*(n+1));
		}
		for(int j = 0; j < n; ++j)
			if(matrix[0][j] == '1')dp[0][j] = 1;

		for(int j = 0; j < n; ++j)
			for(int i = 1; i < m; ++i)
				if(matrix[i][j] == '1') dp[i][j] = dp[i-1][j] + 1;
		int maxArea = 0;
		for(int i = 0; i < m; ++i){
			int tmp = largestRectangleArea(dp[i],n+1);
			if(tmp > maxArea)
				maxArea = tmp;
		}
		for(int i = 0; i < m; ++i)
			delete[] dp[i];
		delete[] dp;
		return maxArea;
    }
};

leetcode - Maximal Rectangle