非交差セットクラス

class DisjSets// 
{
public:
    explicit DisjSets(int numElements);
    int find(int x) const;
    int find(int x);
    void unionSets(int root1,int root2);
    void unionSets2(int root1,int root2);
private:
    vector<int> s;
};
DisjSets::DisjSets(int numElements) : s(numElements)// 
{
    for(int i=0 ; i < s.size() ; i++)
        s[i] = -1;
}
void DisjSets::unionSets(int root1,int root2)
{
    s[root2] = root1;
}
void DisjSets::unionSets2(int root1,int root2)
{
    if( s[root2] < s[root1])
        s[root1] = root2;
    else
    {
        if(s[root1] == s[root2])
            s[root1]--;
        s[root2] = root1;
    }
}
int DisjSets::find(int x) const
{
    if(s[x] < 0)
        return x;
    else
        return find(s[x]);
}

int DisjSets::find(int x) 
{
    if(s[x] < 0)
        return x;
    else
        return s[x] = find(s[x]);
}