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Maximal Rectangle.cpp
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88 lines (81 loc) · 2.51 KB
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class Solution
{
public:
vector<int> calc_width_before(const vector<int>& height)
{
vector<int> width;
if (!height.empty())
{
width.push_back(1);
vector<pair<int, int> > height_width({{height[0], 1}});
for (size_t i = 1; i < height.size(); ++i)
{
if (height[i] > height[i - 1])
{
height_width.push_back(make_pair(height[i], 1));
width.push_back(1);
}
else
{
int w = 1;
while (!height_width.empty() && height_width.back().first >= height[i])
{
w += height_width.back().second;
height_width.pop_back();
}
height_width.push_back(make_pair(height[i], w));
width.push_back(w);
}
}
}
return width;
}
int largestRectangleArea(vector<int>& height)
{
int largest = 0;
vector<int> left_width = calc_width_before(height);
reverse(height.begin(), height.end());
vector<int> right_width = calc_width_before(height);
reverse(right_width.begin(), right_width.end());
reverse(height.begin(), height.end());
for (int i = 0; i < height.size(); ++i)
{
int area = (left_width[i] + right_width[i] - 1) * height[i];
if (area > largest)
{
largest = area;
}
}
return largest;
}
int maximalRectangle(vector<vector<char>>& matrix)
{
int largest = 0;
if (!matrix.empty())
{
size_t rows = matrix.size();
size_t columns = matrix[0].size();
vector<int> height(columns, 0);
for (size_t r = 0; r < rows; ++r)
{
for (size_t c = 0; c < columns; ++c)
{
if (matrix[r][c] == '1')
{
height[c] += 1;
}
else
{
height[c] = 0;
}
}
int temp_largest = largestRectangleArea(height);
if (temp_largest > largest)
{
largest = temp_largest;
}
}
}
return largest;
}
};