【数据结构】并查集

并查集

验证链接：https://www.luogu.com.cn/problem/P3367

同时使用按秩合并和路径压缩的写法，由于使用了按秩合并，所以路径压缩使用递归并不会爆栈。

struct DisjointSet {

    static const int MAXN = 200000 + 10;
    int fnd[MAXN], siz[MAXN];

    void Init(int n) {
        for(int i = 1; i <= n; i++)
            fnd[i] = i, siz[i] = 1;
    }

    int Find(int x) {
        return (fnd[x] == x) ? x : fnd[x] = Find(fnd[x]);
    }

    int Size(int x) {
        x = Find(x);
        return siz[x];
    }

    int Merge(int x, int y) {
        x = Find(x), y = Find(y);
        if(x == y)
            return 0;
        if(siz[x] < siz[y])
            swap(x, y);
        fnd[y] = x;
        siz[x] += siz[y];
        return x;
    }

} ds;

并查集维护可删除链表

struct DisjointSet {

    static const int MAXN = 200000 + 10;
    int prev[MAXN], next[MAXN];

    void Init(int n) {
        for(int i = 0; i <= n + 1; ++i)
            prev[i] = i, next[i] = i;
    }

    int Prev(int x) {
        return (prev[x] == x) ? x : prev[x] = Prev(prev[x]);
    }

    int Next(int x) {
        return (next[x] == x) ? x : next[x] = Next(next[x]);
    }

    void Delete(int x) {
        prev[x] = Prev(x - 1), next[x] = Next(x + 1);
    }

} ds;