#include <bits/stdc++.h>
using namespace std;
#ifdef LOCAL
#include "debug.h"
#else
#define debug(...)
#endif
using pii=array<int,2>;
using tii=array<int,3>;
const int N=300005;
int n,r,a,b,dep[N],p[N],q[N],L[N],pA[N],subA[N];
vector<int> dp[N];
vector<int> dp2[N];
int dp3[N][15],dp4[N][15];
vector<int> g[N],c[N],dA[N];
void dfs0(int u){
L[dep[u]]=u;
if(dep[u]>=a){
pA[u]=L[dep[u]-a];
subA[u]=L[dep[u]-a+1];
dA[pA[u]].push_back(u);
}
int idx=0;
for(int v: g[u]) if(p[u]!=v){
dep[v]=dep[u]+1;
p[v]=u;
q[v]=++idx;
c[u].push_back(v);
dfs0(v);
}
}
int dfs1(int u,int d);
int dfs2(int u,int d);
multiset<int> dp2C[N];
int Get(int u,int k){
int &ret=dp[u][k];
if(ret) return ret;
if(dp2C[u].size()!=dA[u].size()){
for(int i=0;i<(int)dA[u].size();i++){
int v=dA[u][i];
int val=dfs1(v,b),w=v,d=0,e=0;
while(d<b){
e=q[w];
w=p[w];
d++;
val=min(val,Get(w,e));
if(d<b) for(int i=0;i<(int)c[w].size();i++) if(i+1!=e) val=min(val,dfs1(c[w][i],b-d-1));
}
dp2[u][i]=val;
dp2C[u].insert(dp2[u][i]);
}
}
if(dA[u].empty()||(dA[u].size()==1&&k)){
ret=u;
for(int i=0;i<(int)c[u].size();i++) if(i+1!=k) ret=min(ret,dfs2(c[u][i],b-1));
} else{
if(k) dp2C[u].erase(dp2C[u].lower_bound(dp2[u][k-1]));
ret=*dp2C[u].rbegin();
if(k) dp2C[u].insert(dp2[u][k-1]);
}
debug(u,k,ret);
return ret;
}
int dfs1(int u,int d){
if(d>=15) exit(0);
int &ret=dp3[u][d];
if(ret) return ret;
ret=Get(u,0);
if(d>=1) for(int v: c[u]) ret=min(ret,dfs1(v,d-1));
debug(u,d,0,ret);
return ret;
}
int dfs2(int u,int d){
if(d>=15) exit(0);
int &ret=dp4[u][d];
if(ret) return ret;
ret=u;
if(d>=1) for(int v: c[u]) ret=min(ret,dfs2(v,d-1));
debug(u,d,1,ret);
return ret;
}
int main(){
ios::sync_with_stdio(false); cin.tie(0);
cin>>n>>r>>a>>b;
if(a<=b){
cout<<"1\n";
return 0;
}
for(int u,v,i=1;i<n;i++){
cin>>u>>v;
g[u].push_back(v);
g[v].push_back(u);
}
dfs0(r);
for(int i=1;i<=n;i++){
dp[i].resize(c[i].size()+1);
dp2[i].resize(dA[i].size());
}
cout<<Get(r,0);
return 0;
}
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Correct |
18 ms |
49756 KB |
Output is correct |
2 |
Correct |
18 ms |
49764 KB |
Output is correct |
3 |
Correct |
18 ms |
49752 KB |
Output is correct |
4 |
Correct |
18 ms |
49752 KB |
Output is correct |
5 |
Correct |
18 ms |
49756 KB |
Output is correct |
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Correct |
464 ms |
164588 KB |
Output is correct |
2 |
Correct |
339 ms |
160468 KB |
Output is correct |
3 |
Incorrect |
153 ms |
131524 KB |
Output isn't correct |
4 |
Halted |
0 ms |
0 KB |
- |
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Correct |
19 ms |
49752 KB |
Output is correct |
2 |
Incorrect |
19 ms |
49840 KB |
Output isn't correct |
3 |
Halted |
0 ms |
0 KB |
- |
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Correct |
19 ms |
49752 KB |
Output is correct |
2 |
Incorrect |
19 ms |
49840 KB |
Output isn't correct |
3 |
Halted |
0 ms |
0 KB |
- |
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Runtime error |
133 ms |
150344 KB |
Execution killed with signal 6 |
2 |
Halted |
0 ms |
0 KB |
- |
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Correct |
19 ms |
49752 KB |
Output is correct |
2 |
Incorrect |
19 ms |
49840 KB |
Output isn't correct |
3 |
Halted |
0 ms |
0 KB |
- |
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Correct |
18 ms |
49756 KB |
Output is correct |
2 |
Correct |
18 ms |
49764 KB |
Output is correct |
3 |
Correct |
18 ms |
49752 KB |
Output is correct |
4 |
Correct |
18 ms |
49752 KB |
Output is correct |
5 |
Correct |
18 ms |
49756 KB |
Output is correct |
6 |
Correct |
464 ms |
164588 KB |
Output is correct |
7 |
Correct |
339 ms |
160468 KB |
Output is correct |
8 |
Incorrect |
153 ms |
131524 KB |
Output isn't correct |
9 |
Halted |
0 ms |
0 KB |
- |