Submission #623632

#	Time	Username	Problem	Language	Result	Execution time	Memory
623632		Do_you_copy	Commuter Pass (JOI18_commuter_pass)	C++17	100 / 100	451 ms	31600 KiB

commuter_pass

#include <bits/stdc++.h>
#define taskname "test"
#define fi first
#define se second
#define int ll
#define pb push_back
#define faster ios_base::sync_with_stdio(0); cin.tie(0);
using namespace std;
using ll = long long;
using ull = unsigned ll;
using ld = long double;
using pii = pair <int, int>;
using pil = pair <int, ll>;
using pli = pair <ll, int>;
using pll = pair <ll, ll>;
mt19937 Rand(chrono::steady_clock::now().time_since_epoch().count());

ll min(const ll &a, const ll &b){
    return (a < b) ? a : b;
}

ll max(const ll &a, const ll &b){
    return (a > b) ? a : b;
}

//const ll Mod = 1000000007;
//const ll Mod2 = 999999999989;
//only use when required
const int maxN = 1e5 + 1;
const ll inf = 1e15;
int n, m;
int s, t, x, y;
ll dpx[maxN];
ll dpy[maxN];
vector <pii> adj[maxN];
vector <int> trace[maxN];
vector <int> dag[maxN];
bool visited[maxN];
int deg[maxN];
void Dijkstra(int s, vector <ll> &res, bool flag){
    multiset <pii> S;
    fill(res.begin(), res.end(), inf);
    res[s] = 0;
    S.insert({0, s});
    while (!S.empty()){
        auto r = S.begin(); S.erase(S.begin());
        if (res[r->se] != r->fi) continue;
        int u = r->se;
        for (const pii &i: adj[u]){
            int v = i.fi;
            if (res[v] > res[u] + i.se){
                res[v] = res[u] + i.se;
                S.insert({res[v], v});
                if (flag){
                    trace[v].clear();
                    trace[v].pb(u);
                }
            }
            else if (res[v] == res[u] + i.se && flag){
                trace[v].pb(u);
            }
        }
    }
}

void build_dag(int s){
    queue <int> Q;
    Q.push(s);
    while (!Q.empty()){
        int r = Q.front(); Q.pop();
        if (visited[r]) continue;
        visited[r] = 1;
        for (int v: trace[r]){
            dag[v].pb(r);
            if (!visited[v]){
                Q.push(v);
            }
        }
    }
}

void Init(){
    cin >> n >> m >> s >> t >> x >> y;
    for (int i = 1; i <= m; ++i){
        int u, v, w;
        cin >> u >> v >> w;
        adj[u].pb({v, w});
        adj[v].pb({u, w});
    }
    vector <ll> d(n + 1), e(n + 1), f(n + 1);
    Dijkstra(t, d, 1);
    Dijkstra(x, e, 0);
    Dijkstra(y, f, 0);
    build_dag(s);

    for (int i = 1; i <= n; ++i){
    }
    for (int i = 1; i <= n; ++i){
        for (int j: dag[i]) ++deg[j];
        dpx[i] = e[i];
        dpy[i] = f[i];
    }
    queue <int> Q;
    Q.push(t);
    ll ans = e[y];
    while (!Q.empty()){
        int u = Q.front(); Q.pop();
        ans = min(ans, e[u] + dpy[u]);
        for (const int &i: dag[u]){
            dpy[i] = min(dpy[i], dpy[u]);
            if (!--deg[i]){
                Q.push(i);
            }
        }
    }
    for (int i = 1; i <= n; ++i){
        for (int j: dag[i]) ++deg[j];
        dpx[i] = e[i];
        dpy[i] = f[i];
    }
    Q.push(t);
    while (!Q.empty()){
        int u = Q.front(); Q.pop();
        ans = min(ans, dpx[u] + f[u]);
        for (const int &i: dag[u]){
            dpx[i] = min(dpx[i], dpx[u]);
            if (!--deg[i]){
                Q.push(i);
            }
        }
    }
    cout << ans;
}


signed main(){
    if (fopen(taskname".inp", "r")){
        freopen(taskname".inp", "r", stdin);
        freopen(taskname".out", "w", stdout);
    }
    faster;
    ll tt = 1;
    //cin >> tt;
    while (tt--){
        Init();
    }
}

Compilation message (stderr)

commuter_pass.cpp: In function 'int main()':
commuter_pass.cpp:138:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  138 |         freopen(taskname".inp", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~
commuter_pass.cpp:139:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  139 |         freopen(taskname".out", "w", stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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