Submission #817693

#TimeUsernameProblemLanguageResultExecution timeMemory
817693MohamedAhmed04From Hacks to Snitches (BOI21_watchmen)C++17
35 / 100
4610 ms297504 KiB
#pragma GCC optimize("Ofast") #pragma GCC optimize("unroll-loops") #include <bits/stdc++.h> using namespace std ; const int inf = 1e9 ; const int MAX = 3e5 + 10 ; const int K = 30 ; int arr[MAX] ; int n , m , k ; vector< vector<int> >adj(MAX) ; vector<int>v[MAX] ; int watch[MAX] , cycle_sz[MAX] , id[MAX] ; int dist[MAX][K] ; int calc[MAX][205] ; bool check(int node , int child , int tim) { assert(watch[child] != 0) ; int x = watch[node] ; int tim_node = 2e9 ; if(watch[node]) { int cur = tim % cycle_sz[x] ; tim_node = tim + (id[node] - cur + cycle_sz[x]) % cycle_sz[x] ; } int tim_child = -2e9 ; x = watch[child] ; int cur = tim % cycle_sz[x] ; tim_child = tim + (id[child] - cur + cycle_sz[x]) % cycle_sz[x] ; return (tim_child < tim_node-1 || (tim_child == tim_node - 1 && watch[child] != watch[node])) ; } void solve(int src) { for(int i = 1 ; i <= n ; ++i) dist[i][0] = dist[i][1] = inf ; priority_queue< array<int , 3> , vector< array<int , 3> > , greater< array<int , 3> > >q ; dist[src][0] = 0 ; q.push({0 , src , 0}) ; while(!q.empty()) { array<int , 3>a = q.top() ; q.pop() ; int node = a[1] , cost = a[0] , t = a[2] ; if(dist[node][t] < cost) continue ; for(auto &child : adj[node]) { int child2 = child ; int cost2 = cost + 1 ; if((!watch[child2])) { if(cost2 < dist[child2][0]) { dist[child2][0] = cost2 ; q.push({cost2 , child2 , 0}) ; } continue ; } int x = watch[child2] ; if(check(node , child2 , cost)) //handle waiting for some time { int cur = cost % cycle_sz[x] ; cost2 = cost + (id[child2] - cur + cycle_sz[x]) % cycle_sz[x] + 1 ; if(cost2 < dist[child2][1]) { dist[child2][1] = cost2 ; q.push({cost2 , child2 , 1}) ; } } cost2 = cost + 1 ; //handle corridor if(v[x][(cost2 - 1) % cycle_sz[x]] == child2 && v[x][cost2 % cycle_sz[x]] == node) continue ; if(v[x][cost2 % cycle_sz[x]] != child2) //go without waiting { if(cost2 < dist[child2][t]) { dist[child2][t] = cost2 ; q.push({cost2 , child2 , t}) ; } } } } } void solve2(int src) { for(int i = 1 ; i <= n ; ++i) { for(int j = 0 ; j < K ; ++j) dist[i][j] = inf ; } queue< pair<int , int> >q ; dist[src][0] = 0 ; q.push({src , 0}) ; while(!q.empty()) { pair<int , int>p = q.front() ; q.pop() ; int node = p.first , wait = p.second ; int cost = dist[node][wait] , x = watch[node] ; if(node == n) return ; if((!x) || (v[x][calc[cost + 1][cycle_sz[x]]] != node)) { if(wait+1 < K && dist[node][wait+1] == inf) { dist[node][wait+1] = cost + 1 ; q.push({node , wait+1}) ; } } for(auto &child : adj[node]) { int child2 = child ; int cost2 = cost + 1 ; x = watch[child] ; if(x > 0 && v[x][calc[cost2 - 1][cycle_sz[x]]] == child2 && v[x][calc[cost2][cycle_sz[x]]] == node) continue ; if(x > 0 && v[x][calc[cost2][cycle_sz[x]]] == child2) continue ; if(dist[child2][wait] == inf) { dist[child2][wait] = cost2 ; q.push({child2 , wait}) ; } } } } int main() { ios_base::sync_with_stdio(0) ; cin.tie(0) ; cin>>n>>m ; for(int i = 0 ; i < m ; ++i) { int x , y ; cin>>x>>y ; adj[x].push_back(y) ; adj[y].push_back(x) ; } cin>>k ; for(int i = 1 ; i <= k ; ++i) { cin>>cycle_sz[i] ; v[i].resize(cycle_sz[i]) ; for(int j = 0 ; j < cycle_sz[i] ; ++j) { cin>>v[i][j] ; watch[v[i][j]] = i ; id[v[i][j]] = j ; } } bool flag = true ; for(int i = 1 ; i <= n ; ++i) { for(auto &child : adj[i]) flag &= (watch[i] == 0 || watch[child] == 0 || watch[i] == watch[child]) ; } if(flag) //no corridor connects two two different routes { solve(1) ; if(dist[n][0] == inf) cout<<"impossible\n" ; else cout<<dist[n][0]<<"\n" ; } else { for(int j = 1 ; j < 205 ; ++j) { calc[0][j] = 0 ; for(int i = 1 ; i < n + 1000 ; ++i) { calc[i][j] = calc[i-1][j] + 1 ; if(calc[i][j] == j) calc[i][j] = 0 ; } } solve2(1) ; int ans = inf ; for(int i = 0 ; i < K ; ++i) ans = min(ans , dist[n][i]) ; if(ans == inf) cout<<"impossible\n" ; else cout<<ans<<"\n" ; } return 0 ; }
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