[经典算法]并查集

#include <gtest/gtest.h>
#include <vector>

using namespace std;

class UnionFindSet
{
public:
    void MakeSet(int max)
    {
        m_vecId.assign(max,0);
        for (int i=0; i<max; i++)
        {
            m_vecId[i] = i;
        }

        m_nSetsCount = max;
    }

    int Find(int x)
    {
        return m_vecId[x];
    }

    void UnionSet(int x, int y)
    {
        int xId = Find(x);
        int yId = Find(y);

        if (xId == yId)
        {
            return;
        }

        for (unsigned int i=0; i<m_vecId.size(); ++i)
        {
            if (m_vecId[i] == xId)
            {
                m_vecId[i] = yId;
            }
        }

        --m_nSetsCount;
    }

    int Count()
    {
        return m_nSetsCount;
    }

    bool SameSet(int x, int y)
    {
        return (Find(x) == Find(y));
    }

private:

    vector<int> m_vecId;
    int m_nSetsCount;
};

TEST(Algo, tUnionFindSet)
{
    // 测试集合，按照字母大小写来区分
    char SetData[] = {‘A‘,‘b‘,‘C‘,‘E‘,‘d‘,‘e‘,‘F‘};

    UnionFindSet uf;
    uf.MakeSet(7);

    uf.UnionSet(0,2); // A C
    uf.UnionSet(2,3); // C E
    uf.UnionSet(3,6); // E F

    uf.UnionSet(1,4); // b d
    uf.UnionSet(4,5); // d e

    ASSERT_TRUE(uf.SameSet(0,3));
    ASSERT_TRUE(uf.SameSet(6,2));
    ASSERT_TRUE(uf.SameSet(1,5));

    ASSERT_FALSE(uf.SameSet(0,5));
    ASSERT_FALSE(uf.SameSet(2,1));
    ASSERT_FALSE(uf.SameSet(6,4));
}