Submission #146869

#	Time	Username	Problem	Language	Result	Execution time	Memory
146869		MvC	Beads and wires (APIO14_beads)	C++11	28 / 100	234 ms	5376 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,j;
int c,f[nmax][2],rs;
vector<pair<int,int> >a[nmax];
vector<int>id;
void dfs(int x,int p)
{
	f[x][1]=f[x][0]=0;
	for(int i=0;i<a[x].size();i++)
	{
		int y=a[x][i].fr;
		int c=a[x][i].sc;
		if(y==p)continue;
		dfs(y,x);
		if(a[y].size()>1)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[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++)id.pb(i);
	shuffle(id.begin(),id.end(),rng);
	for(i=0;i<min(n,1000);i++)
	{
		dfs(id[i],0);
		rs=max(f[id[i]][0],rs);
		//if((double)clock()/CLOCKS_PER_SEC>0.970)break;
	}
	cout<<rs<<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:29:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<a[x].size();i++)
              ~^~~~~~~~~~~~
beads.cpp:38:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<a[x].size();i++)
              ~^~~~~~~~~~~~

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