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| #include <cstdio>
#include <ctime>
#include <cstdlib>
using namespace std;
const int N = 1e6 + 10;
struct Node
{
int s[2], v, w, sz;
void init (int k)
{ s[0] = s[1] = 0, v = k, w = rand(), sz = 1; }
} tr[N];
int idx, rt;
void pushup(int x) { tr[x].sz = tr[tr[x].s[0]].sz + 1 + tr[tr[x].s[1]].sz; }
int merge(int x, int y)
{
if (!x || !y) return x | y;
if (tr[x].w < tr[y].w)
return tr[x].s[1] = merge(tr[x].s[1], y), pushup(x), x;
return tr[y].s[0] = merge(x, tr[y].s[0]), pushup(y), y;
}
void split(int u, int k, int &x, int &y)
{
if (!u) return void(x = y = 0);
if (tr[u].v <= k) x = u, split(tr[u].s[1], k, tr[u].s[1], y);
else y = u, split(tr[u].s[0], k, x, tr[u].s[0]);
pushup(u);
}
void insert(int k)
{
int x, y;
split(rt, k, x, y);
tr[++idx].init(k);
rt = merge(merge(x, idx), y);
}
void remove(int k)
{
int x, y, z;
split(rt, k, x, z);
split(x, k - 1, x, y);
y = merge(tr[y].s[0], tr[y].s[1]);
rt = merge(merge(x, y), z);
}
int rnk(int k)
{
int x, y;
split(rt, k - 1, x, y);
int res = tr[x].sz + 1;
rt = merge(x, y);
return res;
}
int kth(int u, int k)
{
while (u)
{
if (k <= tr[tr[u].s[0]].sz) u = tr[u].s[0];
else if (k == tr[tr[u].s[0]].sz + 1) return u;
else k -= tr[tr[u].s[0]].sz + 1, u = tr[u].s[1];
}
}
int pre(int k)
{
int x, y;
split(rt, k - 1, x, y);
int res = kth(x, tr[x].sz);
rt = merge(x, y);
return res;
}
int nxt(int k)
{
int x, y;
split(rt, k, x, y);
int res = kth(y, 1);
rt = merge(x, y);
return res;
}
|