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| #include <cstdio>
#include <algorithm>
#include <vector>
using namespace std;
typedef pair<int, int> PII;
const int N = 3e5 + 10;
int n, m;
vector<PII> v;
struct Node
{
int tag;
int p, s[2];
} tr[N];
void reverse(int x)
{
tr[x].tag ^= 1;
swap(tr[x].s[0], tr[x].s[1]);
}
void pushdown(int x)
{
if (tr[x].tag)
{
reverse(tr[x].s[0]);
reverse(tr[x].s[1]);
tr[x].tag = 0;
}
}
bool isroot(int x)
{
return tr[tr[x].p].s[0] != x && tr[tr[x].p].s[1] != x;
}
void rotate(int x)
{
int y = tr[x].p, z = tr[y].p;
int k = tr[y].s[1] == x;
if (!isroot(y))
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;
}
void update(int x)
{
if (!isroot(x))
update(tr[x].p);
pushdown(x);
}
void splay(int x)
{
update(x);
while (!isroot(x))
{
int y = tr[x].p, z = tr[y].p;
if (!isroot(y))
if ((y == tr[z].s[1]) ^ (x == tr[y].s[1]))
rotate(x);
else
rotate(y);
rotate(x);
}
}
void access(int x)
{
int tmp = x;
for (int y = 0; x; y = x, x = tr[x].p)
{
splay(x);
tr[x].s[1] = y;
}
splay(tmp);
}
void makeroot(int x)
{
access(x);
reverse(x);
}
int findroot(int x)
{
access(x);
while (tr[x].s[0])
{
pushdown(x);
x = tr[x].s[0];
}
splay(x);
return x;
}
void split(int x, int y)
{
makeroot(x);
access(y);
}
void link(int x, int y)
{
makeroot(x);
if (findroot(y) != x)
tr[x].p = y;
}
void cut(int x, int y)
{
makeroot(x);
if (findroot(y) == x && tr[y].p == x && !tr[y].s[0])
tr[x].s[1] = tr[y].p = 0;
}
bool check(int x, int y)
{
makeroot(x);
return findroot(y) == x;
}
int main()
{
scanf("%d%d", &n, &m);
for (int i = 1, a, b; i < n; i++)
{
scanf("%d%d", &a, &b);
link(a, b);
}
for (char op[3]; m; m--)
{
scanf("%s", op);
if (op[0] == 'Q')
{
int p, q;
scanf("%d%d", &p, &q);
puts(check(p, q) ? "Yes" : "No");
}
if (op[0] == 'C')
{
int p, q;
scanf("%d%d", &p, &q);
v.push_back(make_pair(p, q));
cut(p, q);
}
if (op[0] == 'U')
{
int x;
scanf("%d", &x);
link(v[x - 1].first, v[x - 1].second);
}
}
return 0;
}
|