Submission #745749

#	Time	Username	Problem	Language	Result	Execution time	Memory
745749		chanhchuong123	Commuter Pass (JOI18_commuter_pass)	C++14	100 / 100	300 ms	20472 KiB

commuter_pass

#include <bits/stdc++.h>
using namespace std;
#define task ""
#define fi first
#define se second
#define MASK(i) (1 << (i))
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
#define BIT(mask, i) ((mask) >> (i) & 1)
#define FOR(i, a, b) for (int i = (a), _b = (b); i <= _b; ++i)
#define FORD(i, a, b) for (int i = (b), _a = (a); i >= _a; --i)

template <typename T1, typename T2> bool minimize(T1 &a, T2 b) {
	if (a > b) {a = b; return true;} return false;
}
template <typename T1, typename T2> bool maximize(T1 &a, T2 b) {
	if (a < b) {a = b; return true;} return false;
}

const int dx[] = {-1, 0, 0, +1};
const int dy[] = {0, -1, +1, 0};

const long long INF = 1e18;
const int MAX = 100100;
int n, m;
int S, T;
int U, V;
long long dpU[MAX];
long long dpV[MAX];
long long d[4][MAX];
vector<pair<int, int>> adj[MAX];

void dijkstra(int t, int s) {
    priority_queue<pair<long long, int>, vector<pair<long long, int>>, greater<pair<long long, int>>> pq;
    for (int i = 1; i <= n; ++i) d[t][i] = INF;
    pq.push({0, s});
    d[t][s] = 0;
    while (pq.size()) {
        long long dist = pq.top().fi;
        int u = pq.top().se;
        pq.pop();
        if (dist != d[t][u]) continue;
        for (pair<int, int> &x: adj[u]) {
            int v = x.fi, w = x.se;
            if (minimize(d[t][v], dist + w))
                pq.push({d[t][v], v});
        }
    }
}

int main() {
	ios_base::sync_with_stdio(false);
	cin.tie(nullptr);

	if (fopen(task".inp", "r")) {
		freopen(task".inp", "r", stdin);
		freopen(task".out", "w", stdout);
	}

    cin >> n >> m;
    cin >> S >> T;
    cin >> U >> V;
    for (int i = 1; i <= m; ++i) {
        int u, v, c; cin >> u >> v >> c;
        adj[u].push_back({v, c});
        adj[v].push_back({u, c});
    }
    dijkstra(0, S); dijkstra(1, T);
    dijkstra(2, U); dijkstra(3, V);
    priority_queue<pair<long long, int>, vector<pair<long long, int>>, greater<pair<long long, int>>> pq;
    for (int i = 1; i <= n; ++i) {
        if (d[0][i] + d[1][i] == d[0][T])
            pq.push({d[0][i], i});
    }
    for (int i = 1; i <= n; ++i) {
        dpU[i] = dpV[i] = INF;
    }
    while (pq.size()) {
        int i = pq.top().se;
        pq.pop();

        minimize(dpU[i], d[2][i]);
        minimize(dpV[i], d[3][i]);
        for (pair<int, int> &x: adj[i]) {
            int j = x.fi, w = x.se;
            if (d[0][i] + w + d[1][j] == d[0][T]) {
                minimize(dpU[j], dpU[i]);
                minimize(dpV[j], dpV[i]);
            }
        }
    }

    long long ans = d[2][V];
    for (int i = 1; i <= n; ++i) {
        if (d[0][i] + d[1][i] == d[0][T]) {
            minimize(ans, dpU[i] + d[3][i]);
            minimize(ans, dpV[i] + d[2][i]);
        }
    }
    cout << ans;
	return 0;
}

Compilation message (stderr)

commuter_pass.cpp: In function 'int main()':
commuter_pass.cpp:56:10: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   56 |   freopen(task".inp", "r", stdin);
      |   ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
commuter_pass.cpp:57:10: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   57 |   freopen(task".out", "w", stdout);
      |   ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~

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