Submission #1241958

#	Time	Username	Problem	Language	Result	Execution time	Memory
1241958		sunit	Commuter Pass (JOI18_commuter_pass)	C++20	0 / 100	178 ms	26472 KiB

commuter_pass

#include<bits/stdc++.h>
#define int long long
#define bl bool
#define db double 
#define fl float 
#define st string  
#define pb push_back
#define pf push_front
#define is insert
#define endl "\n"
#define pba pop_back
#define pfr pop_front
#define ub upper_bound
#define lb lower_bound 
#define fi first 
#define se second 
#define FOR(i, l, r, st) for(int i = l; i <= r; i += st)
#define FOS(i, l, r, sl) for(int i = l; i >= r; i -= sl)
#define mii map<int, int>
#define us unordered_set 
#define pii pair<int, int>
#define vt vector
using namespace std;

const int maxn = 1000005;
const int INF = (int)4e18;

int N, M;
int A, B, C, D;
vt<vt<pii>> adj;
vt<tuple<int,int,int>> edges;

vt<int> dijkstra(int src) {
    vt<int> dist(N+1, INF);
    priority_queue<pii, vt<pii>, greater<pii>> pq;
    dist[src] = 0;
    pq.push({0, src});
    while (!pq.empty()) {
        auto [du, u] = pq.top(); pq.pop();
        if (du > dist[u]) continue;
        for (auto &e : adj[u]) {
            int v = e.fi, w = e.se;
            if (dist[v] > du + w) {
                dist[v] = du + w;
                pq.push({dist[v], v});
            }
        }
    }
    return dist;
}

void suncuti() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    cout.tie(nullptr);
}

void fre() {
    if (fopen("name.INP", "r")) {
        freopen("name.INP", "r", stdin);
        freopen("name.OUT", "w", stdout);
    }
}

main() {
    suncuti();
    fre();

    cin >> N >> M;
    cin >> A >> B;
    cin >> C >> D;

    adj.assign(N+1, {});
    edges.clear();
    edges.reserve(M);
    FOR(i, 1, M, 1) {
        int u, v, w;
        cin >> u >> v >> w;
        adj[u].pb({v, w});
        adj[v].pb({u, w});
        edges.pb({u, v, w});
    }

    vt<int> dA = dijkstra(A);
    vt<int> dB = dijkstra(B);
    vt<int> dC = dijkstra(C);
    vt<int> dD = dijkstra(D);

    int64_t DAB = dA[B];
    int64_t DCD = dC[D];

    vt<vt<pair<int,int>>> dag(N+1);
    vt<int> indeg(N+1, 0);

    for (auto &t : edges) {
        int u, v, w;
        tie(u, v, w) = t;
        if (dA[u] + w + dB[v] == DAB) {
            int64_t ben = DCD - (dC[u] + dD[v]);
            if (ben < 0) ben = 0;
            dag[u].pb({v, (int)ben});
            indeg[v]++;
        }
        if (dA[v] + w + dB[u] == DAB) {
            int64_t ben = DCD - (dC[v] + dD[u]);
            if (ben < 0) ben = 0;
            dag[v].pb({u, (int)ben});
            indeg[u]++;
        }
    }

    vt<int64_t> dp(N+1, -INF);
    queue<int> q;
    FOR(u, 1, N, 1) {
        if (indeg[u] == 0) q.push(u);
    }
    dp[A] = 0;
    while (!q.empty()) {
        int u = q.front(); q.pop();
        for (auto &e : dag[u]) {
            int v = e.fi;
            int64_t ben = e.se;
            if (dp[u] > -INF) dp[v] = max(dp[v], dp[u] + ben);
            if (--indeg[v] == 0) q.push(v);
        }
    }

    int64_t bestBen = dp[B];
    if (bestBen < 0) bestBen = 0;
    int64_t ans = DCD - bestBen;
    cout << ans << endl;

    return 0;
}

Compilation message (stderr)

commuter_pass.cpp:65:1: warning: ISO C++ forbids declaration of 'main' with no type [-Wreturn-type]
   65 | main() {
      | ^~~~
commuter_pass.cpp: In function 'void fre()':
commuter_pass.cpp:60:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   60 |         freopen("name.INP", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
commuter_pass.cpp:61:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   61 |         freopen("name.OUT", "w", stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~

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