Submission #1210842

#	Time	Username	Problem	Language	Result	Execution time	Memory
1210842		loom	Aesthetic (NOI20_aesthetic)	C++20	100 / 100	388 ms	65572 KiB

Aesthetic

#include<bits/stdc++.h>
using namespace std;
#define int long long
#define inf 5e18
#define nl '\n'

const int N = 3e5+1;
vector<tuple<int,int,int>> g[N];
tuple<int,int,int> e[N];
int d1[N], dn[N], p[N];
int n;

void Dijkstra(int s){
   auto &dist = (s == 1 ? d1 : dn);
   priority_queue<pair<int,int>, vector<pair<int,int>>, greater<pair<int,int>>> pq;
   fill(dist, dist+n+1, inf);
   pq.push({0, s});
   dist[s] = 0;

   while(!pq.empty()){
      auto [d, v] = pq.top();
      pq.pop();
      if(dist[v] != d) continue;

      for(auto [ch, w, i] : g[v]){
         if(d + w < dist[ch]){
            dist[ch] = d + w;
            pq.push({dist[ch], ch});
         }
      }
   }
}

int vis[N], tin[N], low[N], tf[N];
vector<int> brg;
int cnt;

int dfs(int v, int p){
   vis[v] = 1;
   tin[v] = low[v] = cnt++;

   int ft = (v == n);
   for(auto [ch, w, i] : g[v]){
      if(!tf[i] or ch == p) continue;
      if(vis[ch]){
         low[v] = min(low[v], tin[ch]);
         continue;
      }

      int res = dfs(ch, v);
      ft |= res;
      low[v] = min(low[v], low[ch]);

      if(res and tin[v] < low[ch]) brg.push_back(i);
   }

   return ft;
}

inline void solve(){
   int m;
   cin>>n>>m;

   for(int i=0; i<m; i++){
      int a, b, w;
      cin>>a>>b>>w;

      g[a].push_back({b, w, i});
      g[b].push_back({a, w, i});
      e[i] = {a, b, w};
   }

   int mx = 0;
   for(int i=m-1; i>=0; i--){
      auto [a, b, w] = e[i];
      p[i] = mx;
      mx = max(mx, w);
   }

   Dijkstra(1);
   Dijkstra(n);

   int lo = d1[n], hi = d1[n] + p[0];
   while(lo < hi){
      int md = (lo+hi+1)/2;

      for(int i=0; i<m; i++){
         auto [a, b, w] = e[i];
         tf[i] = (min(d1[a] + dn[b], d1[b] + dn[a]) + w < md);
      }

      fill(vis, vis+n+1, 0);
      brg.clear();
      cnt = 0;
      dfs(1, 0);

      int pos = !vis[n];
      for(int i : brg){
         auto [a, b, w] = e[i];
         pos |= (min(d1[a] + dn[b], d1[b] + dn[a]) + w + p[i] >= md);
      }

      if(pos) lo = md;
      else hi = md-1;
   }

   cout<<lo;
}

signed main(){
   ios_base::sync_with_stdio(0);
   cin.tie(NULL);cout.tie(NULL);

   int t = 1;
   //cin>>t;
   while(t--) solve();

   return 0;
}

• Subtask 1: 5 / 5
• Subtask 2: 8 / 8
• Subtask 3: 7 / 7
• Subtask 4: 15 / 15
• Subtask 5: 16 / 16
• Subtask 6: 22 / 22
• Subtask 7: 27 / 27