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| #include <cstdio>
using namespace std;
const int N = 1e5 + 10;
struct Node
{
int v, p, s[2], sz;
} tr[N];
bool vis[N];
int n, m, rt, idx;
void pushup(int x)
{
tr[x].sz = tr[tr[x].s[0]].sz + 1 + tr[tr[x].s[1]].sz;
}
void rotate(int x)
{
int y = tr[x].p, z = tr[y].p;
int k = tr[y].s[1] == x;
tr[z].s[tr[z].s[1] == y] = x;
tr[x].p = z;
tr[y].s[k] = tr[x].s[k ^ 1];
tr[tr[x].s[k ^ 1]].p = y;
tr[x].s[k ^ 1] = y;
tr[y].p = x;
pushup(x);
pushup(y);
}
void splay(int x, int k)
{
while (tr[x].p != k)
{
int y = tr[x].p, z = tr[y].p;
if (z != k)
if ((tr[y].s[1] == x) ^ (tr[z].s[1] == y))
rotate(x);
else
rotate(y);
rotate(x);
}
if (!k)
rt = x;
}
void insert(int x)
{
int u = rt, p;
while (u)
{
p = u;
u = tr[u].s[x > tr[u].v];
}
u = ++idx;
if (p)
tr[p].s[x > tr[p].v] = u;
tr[u].v = x;
tr[u].sz = 1;
tr[u].p = p;
splay(u, 0);
}
int pre(int x)
{
int u = rt, res, v = rt;
while (u)
{
v = u;
if (tr[u].v < x)
{
res = u;
u = tr[u].s[1];
}
else
u = tr[u].s[0];
}
splay(v, 0);
return res;
}
int nxt(int x)
{
int u = rt, res, v = rt;
while (u)
{
v = u;
if (tr[u].v > x)
{
res = u;
u = tr[u].s[0];
}
else
u = tr[u].s[1];
}
splay(v, 0);
return res;
}
void remove(int x)
{
int l = pre(x), r = nxt(x);
splay(l, 0);
splay(r, l);
tr[tr[r].s[0]].sz = 0;
tr[tr[r].s[0]].p = 0;
tr[r].s[0] = 0;
splay(r, 0);
}
void init()
{
rt = ++idx;
tr[rt].p = 0;
tr[rt].sz = 1;
tr[rt].v = 0;
insert(n + 1);
}
int top, stk[N];
int main()
{
scanf("%d%d", &n, &m);
init();
for (char op[2]; m; m--)
{
scanf("%s", op);
if (op[0] == 'D')
{
int x;
scanf("%d", &x);
insert(x);
stk[++top] = x;
vis[x] = true;
}
else if (op[0] == 'R')
{
vis[stk[top]] = false;
remove(stk[top--]);
}
else if (op[0] == 'Q')
{
int x;
scanf("%d", &x);
if (vis[x])
puts("0");
else
printf("%d\n", tr[nxt(x)].v - tr[pre(x)].v - 1);
}
}
return 0;
}
|