Submission #1311709

#	Time	Username	Problem	Language	Result	Execution time	Memory
1311709		dex111222333444555	Commuter Pass (JOI18_commuter_pass)	C++20	100 / 100	208 ms	19404 KiB

commuter_pass

#include <bits/stdc++.h>
#define all(v) begin(v), end(v)
#define siz(v) (int)(v).size()
#define ii pair<int, int>
#define ill pair<int, long long>
#define lli pair<long long, int>
#define fi first
#define se second

using namespace std;

template<class X, class Y> bool maximize(X &x, const Y &y){return x < y ? x = y, 1: 0;}
template<class X, class Y> bool minimize(X &x, const Y &y){return x > y ? x = y, 1: 0;}

const int MAXN = 1e5 + 5;
const long long inf = 1e18 + 234;

struct E{
    int u, v, w;

    E(int _u = 0, int _v = 0, int _w = 0):
        u(_u), v(_v), w(_w) {};

    int other(int x){
        return u ^ v ^ x;
    }
};

int numNode, numEdge, in[MAXN], S, T, U, V;
long long distS[MAXN], distT[MAXN], distU[MAXN], distV[MAXN], dpU[MAXN], dpV[MAXN];
vector<int> adj[MAXN], nadj[MAXN];
E edge[MAXN << 1];

void input(){
    cin >> numNode >> numEdge;
    cin >> S >> T >> U >> V;
    for(int i = 1; i <= numEdge; i++){
        int u, v, w; cin >> u >> v >> w;
        adj[u].push_back(i);
        adj[v].push_back(i);
        edge[i] = E(u, v, w);
    }
}

void dijsktra(long long *dist, const int &source){
    priority_queue<lli, vector<lli>, greater<lli> > q;
    memset(dist, 0x3f, (numNode + 1) * sizeof(long long));
    q.push(lli(dist[source] = 0, source));

    while(q.size()){
        long long len = q.top().fi;
        int u = q.top().se;
        q.pop();
        if (len > dist[u]) continue;
        for(int id: adj[u]){
            int v = edge[id].other(u);
            if (minimize(dist[v], dist[u] + edge[id].w))
                q.push(lli(dist[v], v));
        }
    }
}

bool valid(int u, int v, int w){
    if (distS[u] + w + distT[v] == distS[T]) return 1;
    return 0;
}

void addEdge(int u, int v){
    nadj[u].push_back(v);
    in[v]++;
}

void solve(){
    dijsktra(distS, S); dijsktra(distT, T);
    dijsktra(distU, U); dijsktra(distV, V);

    for(int i = 1; i <= numEdge; i++){
        int u = edge[i].u, v = edge[i].v, w = edge[i].w;
        if (valid(u, v, w)) addEdge(u, v);
        if (valid(v, u, w)) addEdge(v, u);
    }

    memset(dpU, 0x3f, sizeof dpU);
    memset(dpV, 0x3f, sizeof dpV);

    long long res = inf;

    queue<int> q;
    for(int u = 1; u <= numNode; u++) if (!in[u]) q.push(u);

    while(q.size()){
        int u = q.front();
        q.pop();

        minimize(dpU[u], distU[u]);
        minimize(dpV[u], distV[u]);

        minimize(res, dpU[u] + distV[u]);
        minimize(res, dpV[u] + distU[u]);

        for(int v: nadj[u]){
            minimize(dpU[v], dpU[u]);
            minimize(dpV[v], dpV[u]);

            if (--in[v] == 0){
                q.push(v);
            }
        }
    }

    cout << res << '\n';
}

int main(){
    ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
    #define task "test"
    if (fopen(task".inp","r")){
        freopen(task".inp", "r", stdin);
        freopen(task".out", "w", stdout);
    }
    input();
    solve();
}

Compilation message (stderr)

commuter_pass.cpp: In function 'int main()':
commuter_pass.cpp:118:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  118 |         freopen(task".inp", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
commuter_pass.cpp:119:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  119 |         freopen(task".out", "w", stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~

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