Submission #685348

#	Time	Username	Problem	Language	Result	Execution time	Memory
685348		saayan007	Commuter Pass (JOI18_commuter_pass)	C++17	31 / 100	247 ms	19500 KiB

commuter_pass

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

using ll = long long;
using pi = pair<int, int>;
using pl = pair<long long, long long>;
using vi = vector<int>;
using vl = vector<long long>;
using vpi = vector<pair<int, int>>;
using vpl = vector<pair<long long, long long>>;

#define fur(i, a, b) for(ll i = a; i <= (ll)b; ++i)
#define ruf(i, a, b) for(ll i = a; i >= (ll)b; --i)
#define fr first 
#define sc second
#define mp make_pair
#define pb emplace_back
#define nl "\n"
#define all(x) (x).begin(),(x).end()
#define rall(x) (x).rbegin(),(x).rend()

const ll mxn = 1e5L + 1;
const ll inf = 1e16L;
ll n, m, s, t, u, v;
vpl adj[mxn];
ll dist[mxn];
bool zer[mxn] = {};

void shortest_path() {
    priority_queue<pl> pq;
    fur(i, 0, n) {
        dist[i] = inf;
    }

    bool proc[n + 1] = {};
    dist[s] = 0;
    pq.emplace(-dist[s], s);
    while(!pq.empty()) {
        ll a = pq.top().sc;
        pq.pop();
        if(proc[a])
            continue;
        proc[a] = 1;

        for(auto [b, c] : adj[a]) {
            if(dist[b] > dist[a] + c) {
                dist[b] = dist[a] + c;
                pq.emplace(-dist[b], b);
            }
        }
    }
}

void nodes() {
    priority_queue<pl> pq;
    pq.emplace(dist[t], t);

    while(!pq.empty()) {
        ll a = pq.top().sc;
        pq.pop();
        if(zer[a])
            continue;
        zer[a] = 1;

        for(auto [b, c] : adj[a]) {
            if(dist[a] - c == dist[b]) {
                pq.emplace(dist[b], b);
            }
        }
    }
}

ll find_answer() {
    ll len[n + 1];
    bool proc[n + 1] = {};
    fur(i, 0, n) {
        len[i] = inf;
    }

    priority_queue<tuple<ll, ll, ll>> pq;
    len[u] = 0;
    pq.emplace(-len[u], u, 0);

    while(!pq.empty()) {
        ll d, a, ten, dir;
        tie(d, a, ten) = pq.top();
        pq.pop();

        if(proc[a])
            continue;
        proc[a] = 1;

        dir = ten % 2;
        ten /= 2;

        for(auto [b, c] : adj[a]) {
            if(ten == 0) {
                // use zero
                if(zer[a] && zer[b]) {
                    if(dist[a] + c == dist[b]) {
                        len[b] = min(len[b], len[a]);
                        pq.emplace(-len[a], b, 3);
                    } 
                    else if(dist[a] - c == dist[b]) {
                        len[b] = min(len[b], len[a]);
                        pq.emplace(-len[b], b, 2);
                    }
                }

                // dont use zero
                if(len[a] + c < len[b]) {
                    len[b] = len[a] + c;
                    pq.emplace(-len[b], b, 0);
                }
            } 

            else if(ten == 1) {
                // continue using
                if(zer[a] && zer[b]) {
                    // check direction
                    if(dist[a] + c * (dir == 1 ? 1 : -1) == dist[b]) {
                        len[b] = min(len[b], len[a]);
                        pq.emplace(-len[b], b, 2 + dir);
                    }
                }

                // stop using
                if(len[a] + c < len[b]) {
                    len[b] = len[a] + c;
                    pq.emplace(-len[b], b, 4);
                }
            } 

            else if(ten == 2) {
                if(len[a] + c < len[b]) {
                    len[b] = len[a] + c;
                    pq.emplace(-len[b], b, 4);
                }
            }
        }
    }
    return len[v];
}
int main() 
{
    ios::sync_with_stdio(0);
    cin.tie(0);

    cin >> n >> m >> s >> t >> u >> v;
    fur(i, 1, m) {
        ll a, b, c;
        cin >> a >> b >> c;
        adj[a].pb(b, c);
        adj[b].pb(a, c);
    }

    shortest_path();
    nodes();
    cout << find_answer();
}

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