【Naive Splay Template】

写小作业的时候重新复习了一下splay
只支持插入，删除，查k大，查节点数。没有迭代器。
T类型需要重载==和<，要调用拷贝构造函数。

template
class Splay {
private:
    struct node {
        T v;
        node *ch[2], *fa;
        int size;
        node(const T &a) : size(1), v(a), ch{nullptr, nullptr}, fa(nullptr) {};
        void setc(node *r, int c) {
            ch[c] = r;
            if (r != nullptr) r->fa = this;
        }
        int pl() {
            if (fa != nullptr) return fa->ch[1] == this;
            else return 0;
        }
        void count() {
            size = 1;
            if (ch[0] != nullptr) size += ch[0]->size;
            if (ch[1] != nullptr) size += ch[1]->size;
        }
    };
    node *root;

    void release(node *r) {
        if (r == nullptr) return;
        release(r->ch[0]);
        release(r->ch[1]);
        delete r;
    }

public:
    Splay() : root(nullptr) {}

    ~Splay() {
        release(root);
    }

private:
    void rotate(node *r) {
        node *f = r->fa;
        int c = r->pl();
        if (f == root) r->fa = nullptr, root = r;
        else f->fa->setc(r, f->pl());
        f->setc(r->ch[c ^ 1], c);
        r->setc(f, c ^ 1);
        f->count();
    }

    void splay(node *r, node *tar = nullptr) {
        for(; r->fa != tar; rotate(r))
            if (r->fa->fa != tar) rotate(r->fa->pl() == r->pl() ? r->fa : r);
        r->count();
    }

    void rm(node *);

public:
    int size();
    
    void remove(const T &);

    void insert(const T &);

    T *kth(int);
};

template
int Splay::size() {
    if (root == nullptr) return 0;
    else return root->size;
}

template
void Splay::rm(node *r) {
    node *f = nullptr;
    if (r->ch[0] == nullptr && r->ch[1] == nullptr) {
        if (r == root) root = nullptr;
        else {
            f = r->fa;
            r->fa->setc(nullptr, r->pl());
            delete r;
        }
    } else if (r->ch[0] == nullptr || r->ch[1] == nullptr) {
        int c = r->ch[0] == nullptr;
        node *t = r->ch[c];
        while (t->ch[c ^ 1] != nullptr) t = t->ch[c ^ 1];
        splay(t, r->fa);
        r->fa->setc(nullptr, c ^ 1);
        f = r->fa;
        delete r;
    } else {
        node *h = r->ch[0], *t = r->ch[1];
        while (h->ch[1] != nullptr)
            h = h->ch[1];
        while (t->ch[0] != nullptr) t = t->ch[0];
        splay(h, r->fa);
        splay(t, h);
        t->setc(nullptr, 0);
        delete r;
        f = t;
    }

    while (f != nullptr) {
        f->count();
        f = f->fa;
    }
}

template
void Splay::remove(const T &a) {
    node *r = root;
    while (r != nullptr) {
        if (r->v == a) {rm(r); break;}
        if (a < r->v) r = r->ch[0];
        else r = r->ch[1];
    }
}

template
void Splay::insert(const T &a) {
    node *r = root;
    node *n = new node(a);
    if (root == nullptr) {
        root = n;
        return;
    }
    while (r != nullptr) {
        if (r->v == a) {delete n; break;}
        if (a < r->v) {
            if (r->ch[0] == nullptr) {
                r->setc(n, 0);
                splay(n);
                break;
            }
            else
                r = r->ch[0];
        } else {
            if (r->ch[1] == nullptr) {
                r->setc(n, 1);
                splay(n);
                break;
            }
            else
                r = r->ch[1];
        }
    }
}

template
T *Splay::kth(int k) {
    node *r = root;
    while (r != nullptr) {
        int l_size = 0;
        if (r->ch[0] != nullptr) l_size = r->ch[0]->size;
        if (l_size >= k) r = r->ch[0];
        else if (l_size + 1 == k) return &r->v;
        else {
            k -= (l_size + 1);
            r = r->ch[1];
        }
    }
    return nullptr;
}

转载于:https://www.cnblogs.com/abclzr/p/10589014.html