#include<bits/stdc++.h>
using namespace std;
const int N=3e5+5;
int n,a,b;
vector<int> g[N],vt[N],res;
int dp[N];
bool ck[N];
pair<int,int> p;
bool kt(int u,int v)
{
if(u==p.first && v==p.second)
return false;
if(u==p.second && v==p.first)
return false;
return true;
}
void dis(int u)
{
ck[u]=true;
if(u==b){
dp[b]=1;
res.push_back(b);
return;
}
for(auto v:g[u]){
if(!ck[v]){
dis(v);
dp[u]|=dp[v];
}
}
if(dp[u])
res.push_back(u);
}
void dfs(int u)
{
vt[u].clear();
dp[u]=1;
for(auto v:g[u]){
if(dp[v]==0 && kt(u,v)){
dfs(v);
vt[u].push_back(dp[v]);
}
}
sort(vt[u].begin(),vt[u].end(),greater<int>());
for(int i=0;i<vt[u].size();i++)
dp[u]=max(dp[u],vt[u][i]+1+i);
}
int main()
{
int now,ans=1e9;
cin>>n>>a>>b;
int x,y;
for(int i=1;i<n;i++){
cin>>x>>y;
g[x].push_back(y);
g[y].push_back(x);
}
dis(a);
int lef=0,rig=res.size()-2,mid;
while(lef<=rig){
mid=(lef+rig)>>1;
memset(dp,0,sizeof(dp));
p={res[mid],res[mid+1]};
dfs(a),dfs(b);
if(dp[a]>dp[b])
rig=mid-1;
else
lef=mid+1;
now=max(dp[a]-1,dp[b]-1);
ans=min(ans,now);
}
cout<<ans;
}
Compilation message
torrent.cpp: In function 'void dfs(int)':
torrent.cpp:50:18: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
50 | for(int i=0;i<vt[u].size();i++)
| ~^~~~~~~~~~~~~
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Incorrect |
4 ms |
15708 KB |
Output isn't correct |
2 |
Halted |
0 ms |
0 KB |
- |
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
377 ms |
31304 KB |
Output is correct |
2 |
Correct |
432 ms |
32964 KB |
Output is correct |
3 |
Correct |
419 ms |
34444 KB |
Output is correct |
4 |
Correct |
381 ms |
34516 KB |
Output is correct |
5 |
Correct |
399 ms |
31568 KB |
Output is correct |
6 |
Correct |
333 ms |
32396 KB |
Output is correct |
7 |
Correct |
329 ms |
36904 KB |
Output is correct |