Submission #500482

#	Time	Username	Problem	Language	Result	Execution time	Memory
500482		dsyz	Ferries (NOI13_ferries)	C++17	0 / 40	252 ms	27068 KiB

ferries

#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define MAXN (1000005)
int main() {
	ios_base::sync_with_stdio(false);cin.tie(0);
	ll N,M;
	cin>>N>>M;
	vector<pair<ll,ll> > fromzero[N];
	vector<pair<ll,ll> > fromn[N];
	for(ll i = 0;i < M;i++){
		ll a,b,c;
		cin>>a>>b>>c;
		a--;
		b--;
		fromzero[a].push_back(make_pair(c,b));
		fromn[b].push_back(make_pair(c,a));
	}
	priority_queue<pair<ll,ll>,vector<pair<ll,ll> >,greater<pair<ll,ll> > > pq;
	ll distfromzero[N];
	ll distfromn[N];
	memset(distfromzero,-1,sizeof(distfromzero));
	memset(distfromn,-1,sizeof(distfromn));
	pq.push(make_pair(0,N - 1));
	distfromn[N - 1] = 0;
	while(!pq.empty()){
		pair<ll,ll> u = pq.top();
		pq.pop();
		if(u.first != distfromn[u.second]){
			continue;
		}
		for(auto a : fromn[u.second]){
			if(distfromn[a.second] == -1 || distfromn[a.second] > u.first + a.first){
				distfromn[a.second] = u.first + a.first;
				pq.push(make_pair(distfromn[a.second],a.second));
			}
		}
	}
	pq.push(make_pair(0,0));
	distfromzero[0] = 0;
	while(!pq.empty()){
		pair<ll,ll> u = pq.top();
		pq.pop();
		if(u.first != distfromzero[u.second]){
			continue;
		}
		vector<ll> v;
		for(auto a : fromzero[u.second]){
			v.push_back(a.first);
		}
		vector<pair<ll,ll> > nodes;
		for(auto a : fromzero[u.second]){
			nodes.push_back(make_pair(distfromzero[u.second] + distfromn[a.second],a.second));
		}
		sort(v.begin(),v.end(),greater<ll>());
		sort(nodes.begin(),nodes.end());
		ll index = 0;
		for(auto a : nodes){
			if(distfromzero[a.second] == -1 || distfromzero[a.second] > u.first + v[index]){
				distfromzero[a.second] = u.first + v[index];
				pq.push(make_pair(distfromzero[a.second],a.second));
				index++;
			}
		}
	}
	ll sum = 0;
	for(ll i = 0;i < N;i++){
		sum = max(sum,distfromzero[i] + distfromn[i]);
	}
	cout<<sum<<'\n';
}

• Subtask 1: 0 / 7
• Subtask 2: 0 / 10
• Subtask 3: 0 / 11
• Subtask 4: 0 / 12