| # | Time | Username | Problem | Language | Result | Execution time | Memory |
|---|---|---|---|---|---|---|---|
| 1068062 | kunzaZa183 | Torrent (COI16_torrent) | C++17 | 0 ms | 0 KiB |
This submission is migrated from previous version of oj.uz, which used different machine for grading. This submission may have different result if resubmitted.
#include <bits/stdc++.h>
using namespace std;
#define int long long
signed main(){
int n,st,ed;
cin>>n>>st>>ed;
st--,ed--;
vector<vector<int>> adj(n);
for(int i =0; i < n-1;i++) {
int x,y;
cin>>x>>y;
x--,y--;
adj[x].push_back(y),adj[y].push_back(x);
}
vector<int> bet(n);
vector<int> path;
function<void(int,int)> fp = [&](int cur,int par) {
path.push_back(cur);
if(cur==ed){
return;
}
for(auto a:adj[cur])
if(a!=par) {
fp(a,cur);
if(path.back()==ed)
return;
}
path.pop_back();
};
fp(st,st);
for(auto a:path)
bet[a] = 1;
auto valv = [&](vector<int> & vi) {
if(vi.empty())
return 0;
sort(vi.begin(),vi.end(),greater<int>());
for(int i = 0; i < vi.size();i++)
vi[i] += i+1;
return *max_element(vi.begin(),vi.end());
};
function<int(int,int)> outdp = [&](int cur,int par) {
vector<int> vi;
for(auto a:adj[cur])
if(a != par && bet[a] == 0)
vi.push_back(outdp(a, cur));
return valv(vi);
};
vector<int> dp(n);
for(int i = 1; i < ((int) path.size()) - 1; i++)
dp[path[i]] = outdp(path[i],path[i]);
multiset<int> sst,sed;
for(auto a:adj[st])
if(bet[a] == 0) {
sst.insert(outdp(a,a));
}
for(auto a:adj[ed])
if(bet[a] == 0) {
sed.insert(outdp(a,a));
}
int minans = n;
multiset<int> vi,vi2;
auto val = [](multiset<int> &msi) {
if(msi.empty())
return 0;
return int(msi.size()) + *msi.begin();
};
vector<int> pcomp1(path.size()),pcomp2(path.size());
multiset<int> idk1,idk2;
for(int i = 1; i < path.size() - 1;i++){
if(i>1) {
idk1.erase(idk1.find(dp[path[i-1]] + i - 2));
idk1.insert(dp[path[i-1]] + i - 1);
}
if(i>0)
idk1.insert(dp[path[i]] + i - 1);
pcomp1[i] = *idk1.rbegin();
}
reverse(path.begin(),path.end());
for(int i = 1; i < path.size() - 1;i++){
if(i>1) {
idk2.erase(idk2.find(dp[path[i-1]] + i - 2));
idk2.insert(dp[path[i-1]] + i - 1);
}
if(i>0)
idk2.insert(dp[path[i]] + i - 1);
pcomp2[i] = *idk2.rbegin();
}
reverse(pcomp2.begin(),pcomp2.end());
// for(auto a:pcomp1)
// cout<<a<<' ';
// cout<<"\n";
// for(auto a:pcomp2)
// cout<<a<<' ';
// cout<<'\n';
reverse(path.begin(),path.end());
// for(auto a:path)
// cout<<dp[a]<<" ";
// cout<<"\n";
for(int i = 0; i < path.size() - 1;i++) {
vector<int> vi1,vi2;
for(auto a:sst)
vi1.push_back(a);
for(auto a:sed)
vi2.push_back(a);
if(i!=0)
vi1.push_back(pcomp1[i]);
if(i!=path.size() - 2)
vi2.push_back(pcomp2[i + 1]);
// for(auto a:vi1)
// cout<<a<<" ";
// cout<<"\n";
// for(auto a:vi2)
// cout<<a<<" ";
// cout<<"\n\n";
minans = min(minans,max(valv(vi1), valv(vi2)));
}
cout<<minans<<"\n";
}