Luogu P3369 【模板】普通平衡树

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int root;
int cntnd;
int fa[MAXn + 10], son[MAXn + 10][2], hig[MAXn + 10];
int val[MAXn + 10], cnt[MAXn + 10], siz[MAXn + 10];
inline void pushup(int id) {
    hig[id] = max(hig[son[id][0]], hig[son[id][1]]) + 1;
    siz[id] = siz[son[id][0]] + siz[son[id][1]] + cnt[id];
}
inline int side(int id) {
    return son[fa[id]][1] == id;
}
inline void rotate(int id) {
    int y = fa[id], z = fa[y], sideid = side(id), s = son[id][sideid ^ 1];
    if (z) {son[z][side(y)] = id;} fa[id] = z;
    son[y][sideid] = s; if (s) {fa[s] = y;}
    son[id][sideid ^ 1] = y; fa[y] = id;
    pushup(y); pushup(id);
}
inline void avl(int id) {
    if (abs(hig[son[id][0]] - hig[son[id][1]]) >= 2) {
        int b = hig[son[id][0]] < hig[son[id][1]], big = son[id][b];
        if (hig[son[big][b]] < hig[son[big][b ^ 1]]) rotate(son[big][b ^ 1]);
        int nwrt = son[id][b];
        rotate(nwrt);
        if (fa[nwrt] == 0) root = nwrt;
    }
}
int top, stk[MAXn + 10];
void Insert(int v) {
    int id = root;
    top = 0;
    while (id) {
        stk[++top] = id;
        if (v < val[id]) id = son[id][0];
        else if (v > val[id]) id = son[id][1];
        else break;
    }
    if (id) {
        ++cnt[id];
        while (top) pushup(stk[top--]);
    } else {
        ++cntnd;
        if (stk[top]) son[stk[top]][v > val[stk[top]]] = cntnd;
        else root = cntnd;
        fa[cntnd] = stk[top];
        hig[cntnd] = 1;
        val[cntnd] = v;
        cnt[cntnd] = 1;
        siz[cntnd] = 1;
        while (top) {
            pushup(stk[top]);
            avl(stk[top]);
            --top;
        }
    }
}
void Delete(int v) {
    int id = root;
    top = 0;
    while (id) {
        stk[++top] = id;
        if (v < val[id]) id = son[id][0];
        else if (v > val[id]) id = son[id][1];
        else break;
    }
    if (id) {
        --cnt[id];
        if (cnt[id]) {
            while (top) pushup(stk[top--]);
        } else {
            if (son[id][0] == 0 && son[id][1] == 0) {
                if (top) --top;
                if (stk[top]) son[stk[top]][val[id] > val[stk[top]]] = 0;
                else root = 0;
            } else if (son[id][0] == 0 || son[id][1] == 0) {
                if (top) --top;
                int s = son[id][son[id][0] == 0];
                if (stk[top]) {
                    son[stk[top]][val[id] > val[stk[top]]] = s;
                    fa[s] = stk[top];
                } else {
                    root = s;
                    fa[s] = 0;
                }
            } else {
                int pre = son[id][0];
                while (pre) {
                    stk[++top] = pre;
                    pre = son[pre][1];
                }
                pre = stk[top--];
                val[id] = val[pre];
                cnt[id] = cnt[pre];
                son[stk[top]][stk[top] != id] = son[pre][0];
                if (son[pre][0]) fa[son[pre][0]] = stk[top];
            }
            while (top) {
                pushup(stk[top]);
                avl(stk[top]);
                --top;
            }
        }
    }
}
int ValtoRank(int v) {
    int id = root, ans = 1;
    while (id) {
        if (v < val[id]) {
            id = son[id][0];
        } else if (v > val[id]) {
            ans += siz[son[id][0]] + cnt[id];
            id = son[id][1];
        } else {
            ans += siz[son[id][0]];
            break;
        }
    }
    return ans;
}
int RanktoId(int rk) {
    int id = root;
    while (true) {
        if (rk <= siz[son[id][0]]) {
            id = son[id][0];
        } else if (rk <= siz[son[id][0]] + cnt[id]) {
            return id;
        } else {
            rk -= siz[son[id][0]] + cnt[id];
            id = son[id][1];
        }
    }
}
int PreId(int v) {
    return RanktoId(ValtoRank(v) - 1);
}
int NexId(int v) {
    return RanktoId(ValtoRank(v + 1));
}