Submission #530984

#	Time	Username	Problem	Language	Result	Execution time	Memory
530984		john_wick	Commuter Pass (JOI18_commuter_pass)	C++14	100 / 100	503 ms	30892 KiB

commuter_pass

#include <bits/stdc++.h>
using namespace std;
#define ll long long int
#define mod 1000000007
#define pb push_back
#define ff first
#define ss second
typedef pair<int,int> pp;
bool com(pp x, pp y){
    if(x.ff == y.ff) return x.ss < y.ss;
    return x.ff < y.ff;
}
ll power(ll x, ll y){
    ll prod = 1;
    while(y){
        if(y & 1) prod = (prod * x) % mod;
        x = (x * x) % mod;
        y /= 2;
    }
    return prod;
}
const int N = 2e5 + 7;
int tc = 1;
vector<pair<int, ll>> vtx[N];
ll ds[N];
void dijsktra(int s, ll *d, int n){
    vector<int> vis(n + 1);
    priority_queue<pair<ll, int>> q;
    q.push({0, s});
    while(!q.empty()){
        ll c = q.top().ff;
        int u = q.top().ss;
        q.pop();
        if(!vis[u]){
            d[u] = -c;
            vis[u] = 1;
            for(auto v : vtx[u]){
                q.push({c - v.ss, v.ff}); 
            }
        }
    }
}
void dijstra2(int s, int t, ll *du, ll *dv, int n, ll &ans){
    vector<int> vis(n + 1);
    ll dp[2][n + 2];
    for(int i = 0; i <= n; i++) dp[0][i] = dp[1][i] = 1e15;
    priority_queue<pair<ll, pair<int, int>>> q;
    q.push({0, {s, 0}});
    while(!q.empty()){
        ll c;
        int node, par;
        c = q.top().first;
        node = q.top().second.first;
        par = q.top().second.second;
        q.pop();

        if (!vis[node]) {
			vis[node] = 1;
			ds[node] = -c;
			dp[0][node] = min(du[node], dp[0][par]);
			dp[1][node] = min(dv[node], dp[1][par]);
			for (auto v : vtx[node]) q.push({c - v.second, {v.first, node}});
		} else if (-c == ds[node]) {
			if (min(du[node], dp[0][par]) + min(dv[node], dp[1][par]) <= dp[0][node] + dp[1][node]) {
				dp[0][node] = min(du[node], dp[0][par]);
				dp[1][node] = min(dv[node], dp[1][par]);
			}
		}

    }
    ans = min(ans, dp[0][t] + dp[1][t]);
}
void solve(){
    int n, m;
    cin >> n >> m;
    int s, t;
    cin >> s >> t;
    int u, v;
    cin >> u >> v;
    for(int i = 0; i < m; i++){
        int uu, vv;
        ll w;
        cin >> uu >> vv >> w;
        vtx[uu].pb({vv, w});
        vtx[vv].pb({uu, w});
    }
    ll du[n + 1], dv[n + 1];
    dijsktra(u, du, n);
    dijsktra(v, dv, n);

    ll ans = du[v];
    dijstra2(s, t, du, dv, n, ans);
    dijstra2(t, s, du, dv, n, ans);
    cout << ans << "\n";
    // cout << "Case #" << tc << ": " << ans + k << "\n";
    // tc++;
}
int main(){
    ios_base::sync_with_stdio(false);
	cin.tie(0);
	cout.tie(0); 
	int t = 1;
	// cin >> t;
	while (t--) 
	    solve();
	return 0; 
}
/*
*/

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