Submission #1087568

#	Time	Username	Problem	Language	Result	Execution time	Memory
1087568		shidou26	Commuter Pass (JOI18_commuter_pass)	C++14	100 / 100	219 ms	26752 KiB

commuter_pass

#include <bits/stdc++.h>
using namespace std;

#define endl '\n'
#define all(v) v.begin(), v.end();

typedef long long ll;
typedef pair<int, int> ii;
typedef pair<ll, int> li;

const int N = 2e5 + 3;
const ll INF = 1e18;

int n, m, a, b, c, d;
vector<ii> adj[N];

bool vst[N];
ll best;
ll dp_one[N], dp_two[N];
vector<ll> one, two, three, four;

bool in_shortest_path(int u, int v, int w) {
    return one[u] + w + two[v] == one[b];
}

void prepare() {

}

void input() {
    cin >> n >> m >> a >> b >> c >> d;

    for(int i = 1; i <= m; i++) {
        int u, v, w; cin >> u >> v >> w;
        adj[u].push_back(ii(v, w));
        adj[v].push_back(ii(u, w));
    }
}

void dijkstra(int node, vector<ll> &d) {
    d.resize(n + 1, INF);
    priority_queue<li, vector<li>, greater<li>> pq;
    d[node] = 0; pq.push(li(0, node));
    while(!pq.empty()) {
        ll cost; int u; tie(cost, u) = pq.top(); pq.pop();
        if(cost > d[u]) continue;
        for(int i = 0; i < (int)adj[u].size(); i++) {
            int v, w; tie(v, w) = adj[u][i];
            if(d[v] > d[u] + w) {
                d[v] = d[u] + w;
                pq.push(li(d[v], v));
            }
        }
    }
}

void dfs(int u) {
    vst[u] = true;
    dp_one[u] = dp_two[u] = INF;
    for(int i = 0; i < (int)adj[u].size(); i++) {
        int v, w; tie(v, w) = adj[u][i];
        if(!in_shortest_path(u, v, w)) continue;
        if(!vst[v]) dfs(v);
        dp_one[u] = min(dp_one[u], dp_one[v]);
        dp_two[u] = min(dp_two[u], dp_two[v]);
    }
    best = min(best, three[u] + dp_two[u]);
    best = min(best, dp_one[u] + four[u]);
    dp_one[u] = min(dp_one[u], three[u]);
    dp_two[u] = min(dp_two[u], four[u]);
}

void process() {
    dijkstra(a, one);
    dijkstra(b, two);
    dijkstra(c, three);
    dijkstra(d, four);

    best = three[d];
    dfs(a);
    cout << best << endl;
}

int main() {
    ios_base::sync_with_stdio(0);
    cin.tie(0);

    #define task "BUS"
    if(fopen(task".INP", "r")) {
        freopen(task".INP", "r", stdin);
        freopen(task".OUT", "w", stdout);
    }else {
//        freopen(task".in", "r", stdin);
//        freopen(task".out", "w", stdout);
    }

    prepare();

    int testcase = 1; // cin >> testcase;
    for(int i = 1; i <= testcase; i++) {
        input();
        process();
    }

    return 0;
}

Compilation message (stderr)

commuter_pass.cpp: In function 'int main()':
commuter_pass.cpp:90:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   90 |         freopen(task".INP", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
commuter_pass.cpp:91:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   91 |         freopen(task".OUT", "w", stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~

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