Submission #245998

#	Time	Username	Problem	Language	Result	Execution time	Memory
245998		LucaDantas	Commuter Pass (JOI18_commuter_pass)	C++17	24 / 100	103 ms	14204 KiB

commuter_pass

#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using pii = pair<int, int>;
using vi = vector<int>;

#ifdef MY_DEBUG_FLAG
template<typename T> void debug(T a) { cerr << a << ' '; }
template<typename T, typename U> void debug(pair<T, U> a) { cerr << a.first << ' ' << a.second << ' '; }
template<typename T> void debug(vector<T> a) { for(auto it : a) debug(it);}
template<typename T> void debug(set<T> a) { for(auto it : a) debug(it);}
#define db(a) cerr << "DEBUG ( " << #a << " == "; debug(a); cerr << ")\n"
#else
#define db(...)
#endif

#define pb push_back
#define eb emplace_back
#define ff first
#define ss second
#define fast ios_base::sync_with_stdio(false), cout.tie(nullptr), cin.tie(nullptr)
#define sz(a) ((int)(a).size())
#define rep(i,a,b) for(int i=(a); i<(b); i++)
#define dec(i,n,a) for(int i=(n); i>=(a); i--)
#define clr(a,v) memset(a, v, sizeof(a))
#define all(a) (a).begin(),(a).end()

constexpr ll inf = 0x3f3f3f3f3f3f3f3f;
constexpr int MAXN = 1e5 + 10;
constexpr int mod = 1000000007;

struct Edge
{
	int u, v, w;
} edges[MAXN];

vector<pii> g[MAXN];

ll dist[MAXN][4]; // 0 -> s, 1 -> t, 2 -> u, 3 -> v

void dijkstra(int s, int k) {
	rep(i,0,MAXN) dist[i][k] = inf;
	priority_queue<pair<ll,int>, vector<pair<ll,int>>, greater<pair<ll,int>>> q;
	q.push({0, s});

	bool mark[MAXN]; clr(mark, 0);

	while(!q.empty()) {
		int u = q.top().ss;
		ll d = q.top().ff;
		q.pop();

		if(mark[u]) continue;
		mark[u] = 1;

		dist[u][k] = d;

		for(auto nxt : g[u]) {
			int v = nxt.ff, w = nxt.ss;
			if(dist[v][k] < d + w || mark[v]) continue;

			q.push({d + w, v});
		}
	}
}

vi dag[MAXN], inv_dag[MAXN], poss;
int grau[MAXN];

int main() {
	int n, m; scanf("%d %d", &n, &m);
	int s, t; scanf("%d %d", &s, &t);
	int u, v; scanf("%d %d", &u, &v);
	rep(i,0,m) {
		int a, b, w; scanf("%d %d %d", &a, &b, &w);
		edges[i] = {a,b,w};
		g[a].pb({b,w});
		g[b].pb({a,w});
	}

	dijkstra(s,0);
	dijkstra(t,1);
	dijkstra(u,2);
	dijkstra(v,3);

	ll menor = dist[t][0];

	rep(i,0,m) {
		int x = edges[i].u, y = edges[i].v, w = edges[i].w;
		if(dist[x][0] > dist[y][0]) swap(x,y);
		if(dist[x][0] + w + dist[y][1] == menor)
			dag[x].pb(y), inv_dag[y].pb(x), grau[y]++, poss.pb(x);
	}

	vi ord;
	queue<int> q;
	for(auto x : poss)
		if(!grau[x]) q.push(x);

	while(!q.empty()) {
		int x = q.front();
		ord.pb(x);
		q.pop();
		for(auto y : dag[x]){
			grau[y]--;
			if(!grau[y]) q.push(y);
		}
	}

	ll d[MAXN]; clr(d,0);

	rep(i,1,n+1) d[i] = dist[i][2];

	for(auto x : ord) {
		for(auto y : dag[x]) {
			dist[y][2] = min(dist[x][2], dist[y][2]);
		}
	}

	reverse(all(ord));

	for(auto x : ord) {
		for(auto y : inv_dag[x]) {
			d[y] = min(d[x], d[y]);
		}
	}

	rep(i,1,n+1) {
		dist[i][2] = min(dist[i][2], d[i]);
	}

	ll ans = inf;

	rep(i,0,n) {
		ans = min(ans, dist[i][2] + dist[i][3]);
	}

	printf("%lld\n", ans);
}

Compilation message (stderr)

commuter_pass.cpp: In function 'int main()':
commuter_pass.cpp:71:17: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  int n, m; scanf("%d %d", &n, &m);
            ~~~~~^~~~~~~~~~~~~~~~~
commuter_pass.cpp:72:17: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  int s, t; scanf("%d %d", &s, &t);
            ~~~~~^~~~~~~~~~~~~~~~~
commuter_pass.cpp:73:17: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  int u, v; scanf("%d %d", &u, &v);
            ~~~~~^~~~~~~~~~~~~~~~~
commuter_pass.cpp:75:21: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   int a, b, w; scanf("%d %d %d", &a, &b, &w);
                ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 0 / 16
• Subtask 2: 0 / 15
• Subtask 3: 24 / 24
• Subtask 4: 0 / 45