Submission #1241952

#	Time	Username	Problem	Language	Result	Execution time	Memory
1241952		sunit	Commuter Pass (JOI18_commuter_pass)	C++20	0 / 100	2094 ms	59876 KiB

commuter_pass

#include<bits/stdc++.h>
#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 = 1e6 + 5;
const int mod = 1e9 + 7;
const int INF = 1e18;

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

int n, m, A, B, C, D;
vt<pii> kt[maxn];         // đồ thị ban đầu
map<pii, int> isVIP;      // đánh dấu cạnh VIP
int trace[maxn];
int dp[maxn];

// Dijkstra để tìm đường từ A đến B
void dijkstra_AB() {
    fill(dp, dp + n + 1, INF);
    memset(trace, -1, sizeof(trace));
    dp[A] = 0;
    priority_queue<pii, vt<pii>, greater<pii>> q;
    q.push({0, A});
    while (!q.empty()) {
        int du = q.top().fi;
        int u = q.top().se;
        q.pop();
        if (du > dp[u]) continue;
        for (auto v : kt[u]) {
            int cost = v.se + dp[u];
            if (cost < dp[v.fi]) {
                dp[v.fi] = cost;
                trace[v.fi] = u;
                q.push({dp[v.fi], v.fi});
            }
        }
    }

    // truy vết từ B ngược về A để đánh dấu cạnh VIP
    int u = B;
    while (trace[u] != -1) {
        int p = trace[u];
        isVIP[{u, p}] = 1;
        isVIP[{p, u}] = 1;
        u = p;
    }
}

// Dijkstra từ C đến D, với VIP = miễn phí
int dijkstra_CD() {
    fill(dp, dp + n + 1, INF);
    dp[C] = 0;
    priority_queue<pii, vt<pii>, greater<pii>> q;
    q.push({0, C});
    while (!q.empty()) {
        int du = q.top().fi;
        int u = q.top().se;
        q.pop();
        if (du > dp[u]) continue;
        for (auto v : kt[u]) {
            int w = isVIP[{u, v.fi}] ? 0 : v.se;
            if (dp[u] + w < dp[v.fi]) {
                dp[v.fi] = dp[u] + w;
                q.push({dp[v.fi], v.fi});
            }
        }
    }
    return dp[D];
}

main() {
    suncuti();

    cin >> n >> m;
    cin >> A >> B;
    cin >> C >> D;

    FOR(i, 1, m, 1) {
        int u, v, w;
        cin >> u >> v >> w;
        kt[u].pb({v, w});
        kt[v].pb({u, w});
    }

    dijkstra_AB();       // bước 1: tìm tuyến VIP
    cout << dijkstra_CD(); // bước 2: tìm đường từ C → D với VIP miễn phí
}

Compilation message (stderr)

commuter_pass.cpp:26:17: warning: overflow in conversion from 'double' to 'int' changes value from '1.0e+18' to '2147483647' [-Woverflow]
   26 | const int INF = 1e18;
      |                 ^~~~
commuter_pass.cpp:94:1: warning: ISO C++ forbids declaration of 'main' with no type [-Wreturn-type]
   94 | main() {
      | ^~~~

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