题面
Sol
做个转化
最开始都是虚边
操作\(1\)就是\(LCT\)里的\(Access\)操作
求的就是路径上虚边的个数+1
然后就好办了
用树链剖分+线段树来维护每个点到根虚边的个数的最大值
操作\(1\)：\(Access\)时虚实边的转换，要把原来连的点的\(Splay\)的最左边的点在原树中的子树所有点+1，再把现在连的点做同样的操作-1
操作\(2\)：单点查询，记\(deep[x]\)为\(x\)到根的虚边个数，那么答案就是\(deep[x]+deep[y]-2*deep[lca]+1\)
操作\(3\)：子树最大值
# include <bits/stdc++.h>
# define RG register
# define IL inline
# define Fill(a, b) memset(a, b, sizeof(a))
using namespace std;
typedef long long ll;
const int _(2e5 + 5);
IL ll Input(){
RG ll x = 0, z = 1; RG char c = getchar();
for(; c < '0' || c > '9'; c = getchar()) z = c == '-' ? -1 : 1;
for(; c >= '0' && c <= '9'; c = getchar()) x = (x << 1) + (x << 3) + (c ^ 48);
return x * z;
}
int size[_], Fa[_], deep[_], top[_], son[_], dfn[_], Index, ed[_], id[_];
int fst[_], nxt[_], to[_], cnt, n, m;
int ch[2][_], fa[_];
int mx[_ << 2], tag[_ << 2];
IL void Add(RG int u, RG int v){
nxt[cnt] = fst[u]; to[cnt] = v; fst[u] = cnt++;
}
# define lson x << 1, l, mid
# define rson x << 1 | 1, mid + 1, r
IL void Build(RG int x, RG int l, RG int r){
if(l == r){
mx[x] = deep[id[l]];
return;
}
RG int mid = (l + r) >> 1;
Build(lson); Build(rson);
mx[x] = max(mx[x << 1], mx[x << 1 | 1]);
}
IL void Modify(RG int x, RG int l, RG int r, RG int L, RG int R, RG int v){
if(L <= l && R >= r){
tag[x] += v, mx[x] += v;
return;
}
RG int mid = (l + r) >> 1;
if(L <= mid) Modify(lson, L, R, v);
if(R > mid) Modify(rson, L, R, v);
mx[x] = max(mx[x << 1], mx[x << 1 | 1]) + tag[x];
}
IL int Query(RG int x, RG int l, RG int r, RG int L, RG int R){
if(L <= l && R >= r) return mx[x];
RG int mid = (l + r) >> 1, ans = 0;
if(L <= mid) ans = Query(lson, L, R);
if(R > mid) ans = max(ans, Query(rson, L, R));
return ans + tag[x];
}
# undef lson
# undef rson
IL void Dfs1(RG int u){
size[u] = 1;
for(RG int e = fst[u]; e != -1; e = nxt[e]){
if(size[to[e]]) continue;
fa[to[e]] = Fa[to[e]] = u, deep[to[e]] = deep[u] + 1;
Dfs1(to[e]);
size[u] += size[to[e]];
if(size[to[e]] > size[son[u]]) son[u] = to[e];
}
}
IL void Dfs2(RG int u, RG int Top){
dfn[u] = ++Index, top[u] = Top, id[Index] = u;
if(son[u]) Dfs2(son[u], Top);
for(RG int e = fst[u]; e != -1; e = nxt[e])
if(!dfn[to[e]]) Dfs2(to[e], to[e]);
ed[u] = Index;
}
IL int LCA(RG int u, RG int v){
while(top[u] ^ top[v]){
if(deep[top[u]] > deep[top[v]]) swap(u, v);
v = Fa[top[v]];
}
return deep[u] > deep[v] ? v : u;
}
IL int Son(RG int x){ return ch[1][fa[x]] == x; }
IL int Isroot(RG int x){ return ch[0][fa[x]] != x && ch[1][fa[x]] != x; }
IL int Find(RG int x){ while(ch[0][x]) x = ch[0][x]; return x; }
IL void Rotate(RG int x){
RG int y = fa[x], z = fa[y], c = Son(x);
if(!Isroot(y)) ch[Son(y)][z] = x; fa[x] = z;
ch[c][y] = ch[!c][x]; fa[ch[c][y]] = y;
ch[!c][x] = y; fa[y] = x;
}
IL void Splay(RG int x){
for(RG int y = fa[x]; !Isroot(x); Rotate(x), y = fa[x])
if(!Isroot(y)) Son(x) ^ Son(y) ? Rotate(x) : Rotate(y);
}
IL void Access(RG int x){
for(RG int y = 0, ff; x; y = x, x = fa[x]){
Splay(x);
if(ch[1][x]) ff = Find(ch[1][x]), Modify(1, 1, n, dfn[ff], ed[ff], 1);
if(y) ff = Find(y), Modify(1, 1, n, dfn[ff], ed[ff], -1);
ch[1][x] = y;
}
}
int main(RG int argc, RG char* argv[]){
n = Input(); m = Input(); Fill(fst, -1);
for(RG int i = 1, x, y; i < n; ++i)
x = Input(), y = Input(), Add(x, y), Add(y, x);
Dfs1(1), Dfs2(1, 1), Build(1, 1, n);
for(RG int i = 1; i <= m; ++i){
RG int opt = Input(), x = Input(), y, ans = 0, lca;
if(opt == 1) Access(x);
else if(opt == 2){
y = Input(), lca = LCA(x, y);
ans = Query(1, 1, n, dfn[x], dfn[x]) + Query(1, 1, n, dfn[y], dfn[y]);
ans -= 2 * Query(1, 1, n, dfn[lca], dfn[lca]);
printf("%d\n", ans + 1);
}
else printf("%d\n", Query(1, 1, n, dfn[x], ed[x]) + 1);
}
return 0;
}