OI-codes/AcWing/950/950.cpp

#include <iostream>

using std::cin;
using std::cout;
using std::endl;

const int N = 1e5 + 5;

int n, min, k, c, ans;
char op;

// Treap

int root, cnt;

struct node {
    int l, r, s, v, k;

    node()
        : l(0), r(0), s(0), v(0), k(rand()) {}

    node(int _v)
        : l(0), r(0), s(1), v(_v), k(rand()) {}
} tr[N];

void pushup(int u) {
    tr[u].s = tr[tr[u].l].s + 1 + tr[tr[u].r].s;
}

std::pair<int, int> split(int p, int k) {
    if (!p)
        return std::make_pair(0, 0);

    if (k <= tr[tr[p].l].s) {
        auto o = split(tr[p].l, k);
        tr[p].l = o.second;
        pushup(p);
        o.second = p;
        return o;
    }

    auto o = split(tr[p].r, k - tr[tr[p].l].s - 1);
    tr[p].r = o.first;
    pushup(p);
    o.first = p;

    return o;
}

std::pair<int, int> splitByValue(int p, int v) {
    if (!p)
        return std::make_pair(0, 0);

    if (v <= tr[p].v) {
        auto o = splitByValue(tr[p].l, v);
        tr[p].l = o.second;
        pushup(p);
        o.second = p;
        return o;
    }

    auto o = splitByValue(tr[p].r, v);
    tr[p].r = o.first;
    pushup(p);
    o.first = p;

    return o;
}

int merge(int x, int y) {
    if (!x || !y)
        return x | y;

    if (tr[x].k > tr[y].k) {
        tr[x].r = merge(tr[x].r, y);
        pushup(x);
        return x;
    }

    tr[y].l = merge(x, tr[y].l);
    pushup(y);

    return y;
}

void insert(int v) {
    auto o = splitByValue(root, v);
    int p = ++cnt;

    tr[p] = node(v);

    root = merge(o.first, merge(p, o.second));
}

int getKth(int k) {
    auto x = split(root, k - 1);
    auto y = split(x.second, 1);

    int r = y.first;

    root = merge(x.first, merge(y.first, y.second));

    return tr[r].v;
}

int main() {
    cin >> n >> min;

    while (n--) {
        cin >> op >> k;

        if (op == 'I') {
            if (k >= min) {
                insert(k - c);
            }
        } else if (op == 'A') {
            c += k;
        } else if (op == 'S') {
            c -= k;
            auto o = splitByValue(root, min - c);
            root = o.second;
            ans += tr[o.first].s;
        } else {  // op == 'F'
            cout << (tr[root].s < k ? -1 : getKth(tr[root].s - k + 1) + c) << endl;
        }
    }

    cout << ans << endl;

    return 0;
}