Submission #146859

#	Time	Username	Problem	Language	Result	Execution time	Memory
146859		MvC	Beads and wires (APIO14_beads)	C++11	0 / 100	8 ms	5112 KiB

beads

#pragma GCC target("avx2")
#pragma GCC optimization("O3")
#pragma GCC optimization("unroll-loops")
#include<bits/stdc++.h>
//#include "boxes.h"
#define rc(x) return cout<<x<<endl,0
#define pb push_back
#define mkp make_pair
#define in insert
#define er erase
#define fd find
#define fr first
#define sc second
typedef long long ll;
typedef long double ld;
const ll INF=0x3f3f3f3f3f3f3f3f;
const ll llinf=(1LL<<61);
const int inf=(1<<30);
const int nmax=2e5+50;
const int mod=1e9+7;
using namespace std;
int n,i,x,y,c,f[nmax][2];
vector<pair<int,int> >a[nmax];
void dfs(int x,int p)
{
	f[x][1]=-1e9;
	for(int i=0;i<a[x].size();i++)
	{
		int y=a[x][i].fr,c=a[x][i].sc;
		if(y==p)continue;
		dfs(y,x);
		if(a[y].size()>1 && f[y][1]>=0)f[x][0]+=max(f[y][0],f[y][1]+c);
		else f[x][0]+=f[y][0];
	}
	for(int i=0;i<a[x].size();i++)
	{
		int y=a[x][i].fr,c=a[x][i].sc;
		if(y==p)continue;
		if(a[y].size()>1 && f[y][0]>=0)f[x][1]=max(f[x][1],f[x][0]-max(f[y][0],f[y][1]+c)+f[y][0]+c);
		else f[x][1]=max(f[x][1],f[x][0]+c);
	}
	//cout<<x<<" "<<f[x][0]<<" "<<f[x][1]<<endl;
}
int main()
{
	//freopen("sol.in","r",stdin);
	//freopen("sol.out","w",stdout);
	//mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
	ios_base::sync_with_stdio(false);cin.tie(0);cerr.tie(0);cout.tie(0);
	cin>>n;
	for(i=1;i<n;i++)
	{
		cin>>x>>y>>c;
		a[x].pb(mkp(y,c));
		a[y].pb(mkp(x,c));
	}
	for(i=1;i<=n;i++)if(a[i].size()==1)x=i;
	dfs(x,0);
	cout<<f[x][0]<<endl;
	return 0;
}

Compilation message (stderr)

beads.cpp:2:0: warning: ignoring #pragma GCC optimization [-Wunknown-pragmas]
 #pragma GCC optimization("O3")
 
beads.cpp:3:0: warning: ignoring #pragma GCC optimization [-Wunknown-pragmas]
 #pragma GCC optimization("unroll-loops")
 
beads.cpp: In function 'void dfs(int, int)':
beads.cpp:27:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<a[x].size();i++)
              ~^~~~~~~~~~~~
beads.cpp:35:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<a[x].size();i++)
              ~^~~~~~~~~~~~

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