Submission #197725

#	Time	Username	Problem	Language	Result	Execution time	Memory
197725		moonrabbit2	Beads and wires (APIO14_beads)	C++17	13 / 100	11 ms	5240 KiB

beads

#include <bits/stdc++.h>
#define fi first
#define se second
using namespace std;
typedef long long ll;
typedef double db;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;
typedef pair<db,db> pdb;
typedef tuple<int,int,int> tii;
typedef vector<vector<ll>> mat;
const ll mod=1e9+7;
const int N=2e5+5;
int n,ans,dp1[N],dp2[N],dp3[N],dp4[N];
vector<pii> g[N];
void dfs(int x,int p){
    vector<int> v1,v2;
    dp2[x]=dp3[x]=dp4[x]=-1e9;
    int s=0;
    for(auto &it : g[x]) if(it.fi!=p){
        int u=it.fi,c=it.se;
        dfs(u,x);
        v1.emplace_back(dp1[u]+c-max({dp1[u],dp2[u],dp3[u]+c}));
        v2.emplace_back(dp2[u]+c-max({dp1[u],dp2[u],dp3[u]+c}));
        dp1[x]+=max({dp1[u],dp2[u],dp3[u]+c,dp4[u]+c});
        s+=max({dp1[u],dp2[u],dp3[u]+c});
    }
    if(p){
        for(auto &it : g[x]) if(it.fi!=p){
            int u=it.fi,c=it.se;
            dp3[x]=max(dp3[x],s-max({dp1[u],dp2[u],dp3[u]+c})+dp1[u]+c);
            dp4[x]=max(dp4[x],s-max({dp1[u],dp2[u],dp3[u]+c})+dp2[u]+c);
        }
    }
    sort(v1.begin(),v1.end()); reverse(v1.begin(),v1.end());
    sort(v2.begin(),v2.end()); reverse(v2.begin(),v2.end());
    if(v1.size()>=2){
        dp2[x]=max(dp2[x],s+v1[0]+v1[1]);
        for(auto &it : g[x]) if(it.fi!=p){
            int u=it.fi,c=it.se;
            int c1=dp1[u]+c-max({dp1[u],dp2[u],dp3[u]+c}),c2=dp2[u]+c-max({dp1[u],dp2[u],dp3[u]+c});
            if(c1==v1[0]) dp2[x]=max(dp2[x],s+v1[1]+c2);
            else dp2[x]=max(dp2[x],s+v1[0]+c2);
            if(c2==v2[0]) dp2[x]=max(dp2[x],s+c1+v2[1]);
            else dp2[x]=max(dp2[x],s+c1+v2[0]);
        }
    }
    //cout<<x<<" : "<<dp1[x]<<" "<<dp2[x]<<" "<<dp3[x]<<" "<<dp4[x]<<"\n";
}
int main(){
    ios::sync_with_stdio(false); cin.tie(0);
	cin>>n;
    for(int u,v,c,i=1;i<n;i++){
        cin>>u>>v>>c;
        g[u].emplace_back(v,c);
        g[v].emplace_back(u,c);
    }
    dfs(1,0);
    cout<<max(dp1[1],dp2[1]);
    return 0;
}

• Subtask 1: 13 / 13
• Subtask 2: 0 / 15
• Subtask 3: 0 / 29
• Subtask 4: 0 / 43