Submission #379564

#	Time	Username	Problem	Language	Result	Execution time	Memory
379564		leu_naut	Commuter Pass (JOI18_commuter_pass)	C++11	0 / 100	10 ms	9836 KiB

commuter_pass

#include <bits/stdc++.h>
 
using namespace std;
 
typedef long long ll;
 
#define FOR(i,a,b) for (int i = a; i <= b; ++i)
#define FORd(i,a,b) for (int i = a;i >= b; --i)
#define pii pair<ll,ll>
#define FastRead ios_base::sync_with_stdio(0); cin.tie(nullptr);
 
const int N = 2e5 + 10;
const ll oo = 1e18;
const int MOD = 1e9 + 7;
 
vector <pii> g[N + 10];
ll n,m,s,t,u,v,ans = oo;
ll vs[N + 10],dp[2][N + 10],du[N + 10],dv[N + 10],ds[N + 10];
 
void dijsktra1(int x, ll arr[])
{
    memset(vs,false,sizeof(vs));
   	priority_queue <pii> pq;
   	pq.push({0,x});
    while (!pq.empty()) {
        ll c,node;
        tie(c,node) = pq.top();
        pq.pop();
        if (!vs[node]) {
            vs[node] = true;
            arr[node] = -c;
            for (pii i : g[node]) pq.push(pii(c - i.first,i.second));
        }
    }
}
 
void dijsktra2(ll x, ll y)
{
    fill(dp[0], dp[0] + N, oo);
    fill(dp[1], dp[1] + N, oo);
    memset(vs,false,sizeof(vs));
    priority_queue <pair <ll,pair <ll,ll>>> pq;
    pq.push(make_pair(0ll,pii(x,0ll)));
    while (!pq.empty()) {
        ll c,node,par; pii p;
        tie(c,p) = pq.top();
        tie(node,par) = p;
        pq.pop();
        if (!vs[node]) {
            vs[node] = true;
            ds[node] = -c;
            dp[0][node] = min(du[node], dp[0][par]);
            dp[1][node] = min(dv[node], dp[1][par]);
            for (pii i : g[node]) pq.push(make_pair(c - i.first,pii(i.second,node)));
        }
        else if (-c == ds[node]) {
			ll so = min(du[node],dp[0][par]), so2 = min(dv[node],dp[1][par]);
			if (so + so2 <= 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][y] + dp[1][y]);
}
 
int main()
{
#ifndef ONLINE_JUDGE
	freopen("input.txt","r",stdin);
	freopen("output.txt","w",stdout);
#endif //ONLINE_JUDGE
	FastRead
	cin >> n >> m >> s >> t >> u >> v;
	FOR(i,1,m) {
		int u,v,w;
		cin >> u >> v >> w;
		g[u].push_back(pii(w,v));
        g[v].push_back(pii(w,u));
	}
	dijsktra1(u,du);
	dijsktra1(v,dv);	
	ans = du[v];
	dijsktra2(s,t);
    dijsktra2(t,s);
	cout << ans;	
}

Compilation message (stderr)

commuter_pass.cpp: In function 'int main()':
commuter_pass.cpp:70:9: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
   70 |  freopen("input.txt","r",stdin);
      |  ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~
commuter_pass.cpp:71:9: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
   71 |  freopen("output.txt","w",stdout);
      |  ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~

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