Submission #900032

#	Time	Username	Problem	Language	Result	Execution time	Memory
900032		1075508020060209tc	Beads and wires (APIO14_beads)	C++14	0 / 100	5 ms	21852 KiB

beads

#pragma GCC optimize("O3")
#include<bits/stdc++.h>
using namespace std;
#define int long long
#define X first
#define Y second
#define SZ(x) (int)(x).size()
int n;
vector<pair<int,int>>e[500005];
int dp[2][300005];
int f[3][300005];

void dfs(int nw,int pa,int tp){
if(e[nw].size()==1&&pa){
    dp[0][nw]=0;
    dp[1][nw]=0;
    return;
}
for(int i=0;i<e[nw].size();i++){
    int v=e[nw][i].first;
    if(v==pa){continue;}
    dfs(v,nw,e[nw][i].second);
}
vector<pair<int,int>>vc;
vector<int>vc2;
vc2.push_back(0);
vc.push_back({0,0});
for(int i=0;i<e[nw].size();i++){
    int v=e[nw][i].first;
    if(v==pa){continue;}
    vc.push_back({dp[0][v],dp[1][v]});
    vc2.push_back(e[nw][i].second);
}
for(int i=0;i<vc.size();i++){
    f[0][i]=-1e12;
    f[1][i]=-1e12;
    f[2][i]=-1e12;
}
f[0][0]=0;
for(int i=1;i<vc.size();i++){
    f[0][i]=max(f[0][i],f[0][i-1]+max(vc[i].first,vc[i].second));
    f[1][i]=max({f[1][i],f[0][i-1]+vc2[i]+vc[i].first,f[1][i-1]+max(vc[i].first,vc[i].second)});
    f[2][i]=max({f[2][i],f[1][i-1]+vc2[i]+vc[i].first,f[2][i-1]+max(vc[i].first,vc[i].second)});
}
dp[0][nw]=max(f[2][vc.size()-1],f[0][vc.size()-1]);
dp[1][nw]=max(dp[0][nw],f[1][vc.size()-1]+tp);
}


signed main(){
cin.tie(0);
ios_base::sync_with_stdio(0);

cin>>n;
for(int i=1;i<=n-1;i++){
    int a;int b;int c;
    cin>>a>>b>>c;
    e[a].push_back({b,c});
    e[b].push_back({a,c});
}

dfs(1,0,-1e12);
int ans=dp[0][1];
dfs(2,0,-1e12);
ans=max(ans,dp[0][2]);
cout<<max(0ll,ans)<<"\n";

}

Compilation message (stderr)

beads.cpp: In function 'void dfs(long long int, long long int, long long int)':
beads.cpp:19:14: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<std::pair<long long int, long long int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   19 | for(int i=0;i<e[nw].size();i++){
      |             ~^~~~~~~~~~~~~
beads.cpp:28:14: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<std::pair<long long int, long long int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   28 | for(int i=0;i<e[nw].size();i++){
      |             ~^~~~~~~~~~~~~
beads.cpp:34:14: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<std::pair<long long int, long long int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   34 | for(int i=0;i<vc.size();i++){
      |             ~^~~~~~~~~~
beads.cpp:40:14: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<std::pair<long long int, long long int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   40 | for(int i=1;i<vc.size();i++){
      |             ~^~~~~~~~~~

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