玄学：Runtime Error - Aborted

#include <iostream>
#include <vector>
using namespace std;

const int N = 1e9;
const int MAXN = 101;  // 55pts

class maxSegTree
{
    struct Node
    {
        int val;
        int ls, rs;
        Node() : val(0), ls(-1), rs(-1) {};
    };
    vector<Node> pool;
    int head;
    void push_up(int now)
    {
        pool[now].val = 0;
        if (pool[now].ls != -1)
            pool[now].val = max(pool[now].val, pool[pool[now].ls].val);
        if (pool[now].rs != -1)
            pool[now].val = max(pool[now].val, pool[pool[now].rs].val);
    }
    int modify(int idx, int val, int s, int t, int now)
    {
        if (now == -1)
        {
            pool.push_back(Node());
            now = pool.size() - 1;
        }
        if (s == t)
        {
            pool[now].val = val;
            return now;
        }
        int mid = (s + t) / 2;
        if (idx <= mid)
            pool[now].ls = modify(idx, val, s, mid, pool[now].ls);
        else
            pool[now].rs = modify(idx, val, mid + 1, t, pool[now].rs);
        push_up(now);
        return now;
    }
    int query(int l, int r, int s, int t, int now)
    {
        if (now == -1)
            return 0;
        if (s >= l && t <= r)
            return pool[now].val;
        int mid = (s + t) / 2;
        int ans = 0;
        if (l <= mid)
            ans = max(ans, query(l, r, s, mid, pool[now].ls));
        if (r > mid)
            ans = max(ans, query(l, r, mid + 1, t, pool[now].rs));
        return ans;
    }
public:
    // void modify(int idx, int val) { head = modify(idx, val, 1, N, head); }
    void modify(int idx, int val) { head = modify(idx, val, 1, N, head); }
    int query(int l, int r)       { return query(l, r, 1, N, head); }
    maxSegTree() : head(-1)       {}
};

maxSegTree f[MAXN][2];
// f[0]: b[i] > b[i - 1], f[1]: b[i] < b[i - 1]
// f[1] <- f[0]: query max[v + 1, N] + 1
// f[0] <- f[1]: query max[1, v - 1] + 1

void solve(int n, int q)
{
    while (q--)
    {
        int op;
        cin >> op;
        if (op == 1)
        {
            int l, r, x;
            cin >> l >> r >> x;
            for (int i = l; i <= r; ++i)
            {
                const int v1 = f[i][0].query(x + 1, N);
                const int v2 = f[i][1].query(1, x - 1);
                f[i][1].modify(x, v1 + 1);
                f[i][0].modify(x, v2 + 1);
            }
        }
        if (op == 2)
        {
            int t;
            cin >> t;
            cout << max(f[t][0].query(1, N), f[t][1].query(1, N)) << "\n";
        }
    }
}