Submission #632723

#	Time	Username	Problem	Language	Result	Execution time	Memory
632723		Alma	Commuter Pass (JOI18_commuter_pass)	C++17	0 / 100	212 ms	28480 KiB

commuter_pass

#include <bits/stdc++.h>
using namespace std;

#define int long long

#define fi first
#define se second
using ll = long long;
using ii = pair<int,int>;

const int INF = 1e9;
const ll LLINF = 1e18;
using vi = vector<int>;
using vvi = vector<vi>;

void setIO (string fileName) {
    ios::sync_with_stdio(false);
    cin.tie(NULL);
    if (fileName != "std") {
        freopen((fileName + ".in").c_str(), "r", stdin);
        freopen((fileName + ".out").c_str(), "w", stdout);
    }
}

int dist;
vi vis;
set<ii> st;
stack<int> stck;
vector<vector<ii>> adj;

int dfs (int u, int t) {
	if (u == t) return 0;
	vis[u] = true;
	int ret = INF;
	for (ii p: adj[u]) {
		int v = p.fi, c = p.se;
		if (!vis[v]) ret = min(ret, c + dfs(v, t));
	}
	return ret;
}

void dfs2 (int u, int t, int d) {
	if (u == t and d == dist) {
		int a = u;
		while (stck.size()) {
			int b = stck.top();
			stck.pop();
			st.insert({a, b});
			a = b;
		}
	}
	vis[u] = true;
	stck.push(u);
	for (ii p: adj[u]) {
		int v = p.fi, c = p.se;
		if (!vis[v]) dfs2(v, t, d + c);
	}
	stck.pop();
}

int dijkstra (int n, int s, int t) {
	vi d(n, LLINF);
	d[s] = 0;
	priority_queue<ii> pq;
	pq.push({0, s});

	while (pq.size()) {
		int u = pq.top().second;
		int di = -pq.top().first;
		pq.pop();
		if (di > d[u]) continue;
		for (ii p: adj[u]) {
			int v = p.fi, c = p.se;
			if (di + c < d[v]) {
				d[v] = di+c;
				pq.push({-di-c, v});
			}
		}
	}
	return d[t];
}

signed main() {
    setIO("std");

    int n, m, s, t, u, v, a, b, c;
	cin >> n >> m >> s >> t >> u >> v;
	adj = vector<vector<ii>>(n);
	s--; t--; u--; v--;
	while (m--) {
		cin >> a >> b >> c;
		a--; b--;
		adj[a].push_back({b, c});
		adj[b].push_back({a, c});
	}

	vis = vi(n, false);
	dist = dfs(s, t);
	vis = vi(n, false);
	dfs2(s, t, 0);

	for (int i = 0; i < n; i++) {
		// cout << i+1 << ": ";
		for (int j = 0; j < (int)adj[i].size(); j++) {
			int k = adj[i][j].fi;
			if (st.find({i, k}) != st.end() or st.find({k, i}) != st.end()) {
				adj[i][j].se = 0;
			}
			// cout << adj[i][j].fi+1 << ' ' << adj[i][j].se << ", ";
		}
		// cout << '\n';
	}

	cout << dijkstra(n, u, v) << '\n';

    return 0;
}

Compilation message (stderr)

commuter_pass.cpp: In function 'void setIO(std::string)':
commuter_pass.cpp:20:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   20 |         freopen((fileName + ".in").c_str(), "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
commuter_pass.cpp:21:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   21 |         freopen((fileName + ".out").c_str(), "w", stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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