Submission #706651

#	Time	Username	Problem	Language	Result	Execution time	Memory
706651		hoangnghiep	Beads and wires (APIO14_beads)	C++14	100 / 100	320 ms	48124 KiB

beads

#include<bits/stdc++.h>
#define int long long
#define f first
#define s second
#define repeat(i,a,b) for(int i=a;i<=b;i++)
#define pb push_back
#define p push
#define pii pair<int,int>
#define piii pair<int,pair<int,int>>
#define vii vector<vector<int>>
#define vi vector<int>
//#define DEBUG
//#define multipletest
using namespace std;
const int LIM=2e5;
const int mod=1e9+7;
const int maxn=20;
const int inf=1e9;
int n,m,x,y,k,t,e,q;
int dx[8]={-1,0,1,0,-1,-1,1,1};
int dy[8]={0,1,0,-1,1,-1,1,-1};
char c;
string s;
int a[LIM+5],factorial[(1<<maxn)+5],inv_fact[(1<<maxn)+5];
bool notprime[LIM+5];
map<int,int> mp;
char grid[100+5][100+5];
vector<pii> adj[LIM+5];
int power(int a,int b){
   if(b==0) return 1;
    int t=power(a,b/2);
    t = t * t %mod;
    if(b%2==1) t = t * a %mod;
    return t;
}
bool check(int x,int y){
    if(x<=0 || x>n || y<=0 || y>m || grid[x][y]=='T'){
   return false;
     }
    return true;
}
class DSU{
	int *parent;
	int *rank;
	int *tot;
	public:
	DSU(int n){
		rank=new int[n+5];
		parent=new int[n+5];
		tot=new int [n+5];
		for(int i=0;i<n+5;i++){
			parent[i]=i;
			rank[i]=0;
			tot[i]=1;
		}
	}
	int find(int i){
		if(parent[i]==i){
			return i;
		}
		return parent[i]=find(parent[i]);
	}
	void unite(int u,int v){
		int i=find(u);
		int j=find(v);
		if(i!=j){
			if(rank[i]>rank[j]){
				parent[j]=i;
				tot[i]+=tot[j];
			}
			else if(rank[i]<rank[j]){
				parent[i]=j;
				tot[j]+=tot[i];
			}
			else{
				parent[j]=i;
				rank[i]++;
				tot[i]+=tot[j];
			}
		}
	}
	int total(int u){
	   return tot[u];
	}
};
void precal(int n){
	factorial[0]=1;
	inv_fact[0]=1;
    for (int i = 1; i <n; ++i)
	{
		factorial[i] = factorial[i - 1] * i % mod;
		inv_fact[i] = inv_fact[i - 1] * power(i, mod - 2) % mod;
	}
}
int choose(int n,int k){
	if(k<0 || k>n) return 0;
	return factorial[n] * inv_fact[n-k] % mod * inv_fact[k] %mod;
}
void Sieve(){
	notprime[0]=notprime[1]=true;
    for(int i=2;i<LIM+5;++i){
    	if(notprime[i]==false){
    	for(int j=i*i;j<LIM+5;j+=i){
    		notprime[j]=true;
		}
    }
	}
}
int f[LIM+5][2];
multiset<int> tp[LIM+5];
int ans;
void dfs(int u,int parent){
	int tmp;
	for(auto [v,w] : adj[u]){
		if(parent!=v){
		dfs(v,u);
	   tmp=max(f[v][0],f[v][1]+w);
		f[u][0]+=tmp;
		tp[u].insert(f[v][0]+w-tmp);
	   }
	}
	if(tp[u].empty()) f[u][1]=-inf;
	else f[u][1]=f[u][0] + *rbegin(tp[u]);
}
void dp(int u,int parent){
	int f_u[2],f_v[2],tmp,numv,numu;
	memcpy(f_u,f[u],8);
	ans=max(ans,f[u][0]);
	for(auto [v,w]:adj[u]){
		if(v!=parent){
			f[u][0]-=tmp=max(f[v][0],f[v][1]+w);
			numu=f[v][0]+w-tmp;
			tp[u].erase(tp[u].find(f[v][0]+w-tmp));
			f[u][1]=tp[u].empty()?-inf:f[u][0]+*rbegin(tp[u]);
			memcpy(f_v,f[v],sizeof(f[v]));
			f[v][0]+=tmp=max(f[u][0],f[u][1]+w);
			numv=f[u][0]+w-tmp;
			tp[v].insert(f[u][0]+w-tmp);
			f[v][1]=f[v][0]+ *rbegin(tp[v]);
			dp(v,u);
			memcpy(f[u],f_u,sizeof(f_u));
			memcpy(f[v],f_v,sizeof(f_v));
			tp[u].insert(numu);
			tp[v].erase(tp[v].find(numv));
		}
	}
}
void solve(){
//Sieve();
//   precal();
    cin>>n;
    for(int i=0;i<n-1;++i){
    	int u,v,w;
    	cin>>u>>v>>w;
    	adj[u].push_back({v,w});
    	adj[v].push_back({u,w});
	}
  dfs(1,0);
  dp(1,0);
   cout<<ans<<endl;
}
signed main(){
  // freopen(".inp","r",stdin);
  // freopen(".out","w",stdout);
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
	int test;
	test=1;
	#ifdef multipletest
	cin>>test;
	#endif
	while(test--){
        solve();
        #ifdef DEBUG
		cerr << "Runtime is: " << clock() * 1.0 / CLOCKS_PER_SEC << endl;
	    #endif
	}
}

Compilation message (stderr)

beads.cpp: In function 'void dfs(long long int, long long int)':
beads.cpp:114:11: warning: structured bindings only available with '-std=c++17' or '-std=gnu++17'
  114 |  for(auto [v,w] : adj[u]){
      |           ^
beads.cpp: In function 'void dp(long long int, long long int)':
beads.cpp:129:11: warning: structured bindings only available with '-std=c++17' or '-std=gnu++17'
  129 |  for(auto [v,w]:adj[u]){
      |           ^

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