Submission #519182

#	Time	Username	Problem	Language	Result	Execution time	Memory
519182		MOUF_MAHMALAT	Torrent (COI16_torrent)	C++14	100 / 100	646 ms	27712 KiB

torrent

#include<bits/stdc++.h>
#define all(s) s.begin(),s.end()
#define F first
#define S second
using namespace std;
typedef int ll;
ll n,a,b,op,x,y,dp[300009],pp[300009],ans;
vector<vector<ll> >v;
vector<ll>bin;
inline void dfs(ll d,ll p)
{
    pp[d]=p;
    for(auto&z:v[d])
        if(z!=p)
            dfs(z,d);
}
inline void best(ll d,ll p)
{
    dp[d]=0;
    vector<ll>o;
    for(auto&z:v[d])
    {
        if(z==p||(d==x&&z==y)||(d==y&&z==x))
            continue;
        best(z,d);
        o.push_back(dp[z]);
    }
    sort(all(o),greater<ll>());
    for(ll i=0; i<o.size(); i++)
        dp[d]=max(dp[d],o[i]+i+1);
}
int main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0),cout.tie(0);
    cin>>n>>a>>b;
    v.resize(n+1);
    for(ll i=1; i<n; i++)
    {
        cin>>x>>y;
        v[x].push_back(y);
        v[y].push_back(x);
    }
    dfs(a,0);
    x=b;
    while(x)
    {
        bin.push_back(x);
        x=pp[x];
    }
    reverse(all(bin));
    x=bin[0],y=bin[1];
    best(a,0),best(b,0);
    ans=max(dp[a],dp[b]);
    ll l=0,r=bin.size()-1,m;
    while(r-l>1)
    {
        m=(l+r)>>1;
        x=bin[m];
        y=bin[m+1];
        best(a,0);
        best(b,0);
        op=max(dp[a],dp[b]);
        if(ans<op)
            r=m;
        else
            l=m,ans=op;
    }
    r=l+1,l=0;
    while(r-l>1)
    {
        m=(l+r)>>1;
        x=bin[m-1];
        y=bin[m];
        best(a,0);
        best(b,0);
        op=max(dp[a],dp[b]);
        if(ans<op)
            l=m;
        else
            r=m,ans=op;
    }
    cout<<ans;
    return 0;
}

Compilation message (stderr)

torrent.cpp: In function 'void best(ll, ll)':
torrent.cpp:29:18: warning: comparison of integer expressions of different signedness: 'll' {aka 'int'} and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   29 |     for(ll i=0; i<o.size(); i++)
      |                 ~^~~~~~~~~

• Subtask 1: 31 / 31
• Subtask 2: 69 / 69