LeetCode: Maximal Rectangle

这道题把二维图转换成行数个的柱状图题，就简单了

class Solution {
public:
    int maximalRectangle(vector<vector<char> > &matrix) {
        int x = matrix.size();
        if(0 == x)    return 0;
        int y = matrix[0].size();
        if(0 == y)    return 0;
        vector<vector<int> > result(x, vector<int>(y));
        for(int i = 0; i < x; ++i)
            for(int j = 0; j < y; ++j)
                result[i][j] = '0' == matrix[i][j]? 0: 1;
        for(int i = 1; i < x; ++i)
            for(int j = 0; j < y; ++j)
                result[i][j] += 0 == result[i][j]? 0: result[i-1][j];
        int ret = 0;
        for(int i = 0; i < x; ++i)
            ret = max(ret, maxArea(result[i]));
        return ret;
    }

    int maxArea(vector<int>& line)
    {
        stack<int> S;
        line.push_back(0);
        int sum = 0;
        for (int i = 0; i < line.size(); i++) {
            if (S.empty() || line[i] > line[S.top()]) S.push(i);
            else {
                int tmp = S.top();
                S.pop();
                sum = max(sum, line[tmp]*(S.empty()? i : i-S.top()-1));
                i--;
            }
        }
        return sum;
    }
};

 C#

public class Solution {
    public int MaximalRectangle(char[,] matrix) {
        int m = matrix.GetLength(0);
        int n = matrix.GetLength(1);
        if (m == 0 || n == 0) return 0;
        int[,] result = new int[m, n];
        for (int i = 0; i < m; i++) {
            for (int j = 0; j < n; j++) {
                result[i, j] = '0' == matrix[i, j]? 0 : 1;
            }
        }
        for (int i = 1; i < m; i++) {
            for (int j = 0; j < n; j++) {
                result[i, j] += 0 == result[i, j]? 0 : result[i-1, j];
            }
        }
        int ans = 0;
        for (int i = 0; i < m; i++) {
            ans = Math.Max(ans, maxArea(result, i));
        }
        return ans;
    }
    public int maxArea(int[,] result, int line) {
        Stack<int> S = new Stack<int>();
        List<int> lineCopy = new List<int>();
        for (int i = 0; i < result.GetLength(1); i++) lineCopy.Add(result[line, i]);
        lineCopy.Add(0);
        int sum = 0;
        for (int i = 0; i < lineCopy.Count; i++) {
            if (S.Count == 0 || lineCopy[i] > lineCopy[S.Peek()]) S.Push(i);
            else {
                int peek = S.Peek();
                S.Pop();
                sum = Math.Max(sum, lineCopy[peek] * (S.Count == 0? i : i - S.Peek() - 1));
                i--;
            }
        }
        return sum;
    }
}