Submission #298761

#	Time	Username	Problem	Language	Result	Execution time	Memory
298761		errorgorn	Beads and wires (APIO14_beads)	C++14	100 / 100	855 ms	125296 KiB

beads

//雪花飄飄北風嘯嘯
//天地一片蒼茫

#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,avx2,fma")
#pragma GCC optimize("Ofast")
#pragma GCC optimize("unroll-loops")

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#include <ext/rope>
using namespace std;
using namespace __gnu_pbds;
using namespace __gnu_cxx;
#define ll long long
#define ii pair<ll,ll>
#define iii pair<ii,ll>
#define fi first
#define se second
#define endl '\n'
#define debug(x) cout << #x << " is " << x << endl

#define rep(x,start,end) for(auto x=(start)-((start)>(end));x!=(end)-((start)>(end));((start)<(end)?x++:x--))
#define all(x) (x).begin(),(x).end()
#define sz(x) (int)(x).size()

#define indexed_set tree<ll,null_type,less<ll>,rb_tree_tag,tree_order_statistics_node_update>
//change less to less_equal for non distinct pbds, but erase will bug

mt19937 rng(chrono::system_clock::now().time_since_epoch().count());

struct custom_hash {
    typedef unsigned long long ull;
    const ull FIXED_RANDOM = chrono::steady_clock::now().time_since_epoch().count();
    static ull splitmix64(ull x) {
        // http://xorshift.di.unimi.it/splitmix64.c
        x += 0x9e3779b97f4a7c15;
        x = (x ^ (x >> 30)) * 0xbf58476d1ce4e5b9;
        x = (x ^ (x >> 27)) * 0x94d049bb133111eb;
        return x ^ (x >> 31);
    }

    size_t operator()(ll x) const {
        return splitmix64(x + FIXED_RANDOM);
    }
    size_t operator()(const pair<int,int> &i)const{
        return splitmix64((((ll)i.first)^(((ll)i.second)<<32))+FIXED_RANDOM);
    }
};


int n;
vector<ii> al[200005];
unordered_map<ii,ii,custom_hash> memo;
unordered_map<ii,ll,custom_hash> w;

ii s[200005];
int pa[200005];
ll tot[200005];

ii dp(int i,int p){
	if (memo.count(ii(i,p))) return memo[ii(i,p)];
	
	ii res;
	if (!pa[i]){
		for (auto &it:al[i]){
			if (it.fi==p) continue;
			
			auto temp=dp(it.fi,i);
			ll val=max(temp.fi,temp.se+it.se);
			
			tot[i]+=val;
			
			ll vv=temp.fi+it.se-val;
			if (s[i].fi<vv){
				s[i].se=s[i].fi;
				s[i].fi=vv;
			}
			else if (s[i].se<vv){
				s[i].se=vv;
			}
		}
		res=ii(tot[i],tot[i]+s[i].fi);
		pa[i]=p;
	}
	else{
		if (pa[i]!=-1){
			auto temp=dp(pa[i],i);
			ll ww=w[ii(i,pa[i])];
			ll val=max(temp.fi,temp.se+ww);
			
			tot[i]+=val;
			
			ll vv=temp.fi+ww-val;
			if (s[i].fi<vv){
				s[i].se=s[i].fi;
				s[i].fi=vv;
			}
			else if (s[i].se<vv){
				s[i].se=vv;
			}
			pa[i]=-1;
		}
		
		ii temp;
		ll ww;
		ll val;
		ll vv;
		if (p!=-1){
			temp=dp(p,i);
			ww=w[ii(i,p)];
			val=max(temp.fi,temp.se+ww);
			
			tot[i]-=val;
			vv=temp.fi+ww-val;
		}
		
		res=ii(tot[i],tot[i]+(s[i].fi==vv?s[i].se:s[i].fi));
		
		if (p!=-1){
			tot[i]+=val;
		}
	}
	
	return memo[ii(i,p)]=res;
}

int main(){
	ios::sync_with_stdio(0);
	cin.tie(0);
	cout.tie(0);
	cin.exceptions(ios::badbit | ios::failbit);
	
	memo.reserve(4096);
	memo.max_load_factor(0.25);
	
	w.reserve(4096);
	w.max_load_factor(0.25);
	
	rep(x,0,200005) s[x]=ii(-1e9,-1e9);
	
	cin>>n;
	
	int a,b,c;
	rep(x,1,n){
		cin>>a>>b>>c;
		
		al[a].push_back(ii(b,c));
		al[b].push_back(ii(a,c));
		w[ii(a,b)]=c;
		w[ii(b,a)]=c;
	}
	
	ll ans=0;
	rep(x,1,n+1) ans=max(ans,dp(x,-1).fi);
	
	cout<<ans<<endl;
}

Compilation message (stderr)

beads.cpp: In function 'std::pair<long long int, long long int> dp(int, int)':
beads.cpp:118:36: warning: 'vv' may be used uninitialized in this function [-Wmaybe-uninitialized]
  118 |   res=ii(tot[i],tot[i]+(s[i].fi==vv?s[i].se:s[i].fi));
      |                        ~~~~~~~~~~~~^~~~~~~~~~~~~~~~~

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