找到矩形的边界集

Question

我有 std::vector 个 rectangle 个。 class 的定义很简单：

class rectangle
{
public:
    rectangle();
    rectangle(int leftX, int topY, int width, int height);
    rectangle(const rectangle &other);

    int x() const;
    int y() const;

    int width() const;
    int height() const;

    // Returns the bounding rectangle of this rectangle and the given rectangle.
    rectangle united(const rectangle &r) const;
    rectangle intersected(const rectangle &r) const;

    // Returns true if rectangle intersects with given rectagle else false.
    bool intersects(const rectangle &r) const;
};

对于每个矩形，我想看看是否与向量中的另一个矩形相交，然后 'unite' 它们（找到边界矩形）如果它们相交。

我很想知道是否有办法使用 <algorithm> 中的函数对一系列矩形执行 search/combining。谁能就可能的解决方案提出建议？寻找简洁而不需要重新发明轮子的东西。

[编辑:] 我应该提到我已经实施了 'intersects()' 和 'united'.

我的最终目标是实现一个适用于我的矩形范围的函数，如下所示：

/// For each rectangle in the vector it test if it intersects with another and return the set of united rectangles. 
/// \param v A set of rectangles
/// \return A united set of rectangles.
std::vector<rectangle> test_intersect_and_unite(const std::vector<rectangle> &v)
{
    std::vector<rectangle> united;

    // ...

    return united;
}

我可能处理不到 20 个矩形。

Answer 1

我的问题似乎比答案引起了更多的困惑。也许我不太善于解释自己。尽管如此，这是我（天真的）解决方案。

///////////////////////////////////////////////////////////////////////////
template<template <typename, typename = std::allocator<rectangle>> class Container>
Container<rectangle> test_intersect_and_unite(const Container<rectangle> &v)
{
    Container<rectangle> vTemp{v};

    for (std::size_t i = 0; i < vTemp.size(); ++i)
    {
        for (std::size_t j = 0; j < vTemp.size(); ++j)
        {
            if (i == j) { continue; }

            if (vTemp[i].intersects(vTemp[j]))
            {
                vTemp[i]  = vTemp[i].united(vTemp[j]);
                vTemp.erase(vTemp.begin() + j);
                if (j < i) { --i; }
                --j;
                continue;
            }
        }
    }

    return vTemp;
}

一些简单的单元测试：

////////////////////////////////////////////////////////////////////////////////
class rectangle_utils_test : public testing::Test
{
public:

    rectangle_utils_test() = default;

    ~rectangle_utils_test() override = default;
};


//////////////////////////////////////////////////////////////////////////
TEST_F(rectangle_utils_test, test_intersect_and_unite)
{
    // TODO: This unit test makes some naive assumptions about ordering.
    // TODO: Test with negative values.

    {
        std::vector<rectangle> vArg = {{10, 10, 10, 10}, {15, 15, 10, 10}};

        std::vector<rectangle> v = test_intersect_and_unite(vArg);

        ASSERT_EQ(v.size(), 1);
        ASSERT_EQ(v[0], rectangle(10, 10, 15, 15));
    }

    {
        std::vector<rectangle> vArg = {{10, 10, 10, 10}, {21, 21, 10, 10}};

        std::vector<rectangle> v = test_intersect_and_unite(vArg);

        ASSERT_EQ(v.size(), 2);
        ASSERT_EQ(v[0], rectangle(10, 10, 10, 10));
        ASSERT_EQ(v[1], rectangle(21, 21, 10, 10));
    }

    {
        std::vector<rectangle> vArg = {{10, 10, 10, 10},
                                       {15, 15, 10, 10},
                                       {60, 60, 10, 10},
                                       {5,  5,  10, 10},
                                       {0,  0,  10, 10},
                                       {40, 40, 10, 10}};

        std::vector<rectangle> v = test_intersect_and_unite(vArg);

        ASSERT_EQ(v.size(), 3);
        ASSERT_EQ(v[0], rectangle(0, 0, 25, 25));
        ASSERT_EQ(v[1], rectangle(60, 60, 10, 10));
        ASSERT_EQ(v[2], rectangle(40, 40, 10, 10));
    }

    // Most interesting test case.
    {
        std::vector<rectangle> vArg = {{0,  0,  10, 10},
                                      {20, 20, 10, 10},
                                      {10, 10, 10, 10},
                                      {5,  5,  10, 10},
                                      {15, 15, 10, 10},
                                      {40, 40, 10, 10}};

        std::vector<rectangle> v = test_intersect_and_unite(vArg);

        ASSERT_EQ(v.size(), 2);
        ASSERT_EQ(v[0], rectangle(0, 0, 30, 30));
        ASSERT_EQ(v[1], rectangle(40, 40, 10, 10));
    }
}

找到矩形的边界集

Find bounding set of rectangles

c++

stl-algorithm