并查集

实现的功能：管理元素所属集合

洛谷模板题：Luogu P3367

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#include <bits/stdc++.h>
using namespace std;

typedef long long ll;

class DSU{
private:
    vector<ll> parents, size;
public:
    explicit DSU(ll n) : parents(n + 1), size(n + 1, 1) { iota(parents.begin(), parents.end(), 0); }
    ll find(ll x) { return (parents[x] == x) ? x : (parents[x] = find(parents[x])); }
    void merge(ll a, ll b)
    { // merge a and b
        a = find(a);
        b = find(b);
        if (a == b) return;
        //启发式合并，定向merge删去，merge a -> b
        if (size[a] > size[b]) swap(a, b); 
        parents[a] = b;
        size[b] += size[a];
    }
};

int main()
{
    ios::sync_with_stdio(false);
    cin.tie(0); cout.tie(0);

    ll n, m;
    cin >> n >> m;
    DSU dsu(n);
    while (m--)
    {
        ll opt, a, b;
        cin >> opt >> a >> b;
        if (opt == 1) // merge
            dsu.merge(a, b);
        else // query
            cout << (dsu.find(a) == dsu.find(b) ? "Y" : "N") << endl;
    }
    return 0;
}