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  1. #include<bits/stdc++.h>
  2.  
  3. const int N = 2e5 + 10;
  4. const int V = 1e6 + 10;
  5. const long long M = 1e9 + 7;
  6. const long long INF = 1e18;
  7.  
  8. long long a[N + 1],n,m;
  9. long long fact[N + 1];
  10. std::vector<int> adj[N + 1];
  11.  
  12. void readData(){
  13.     std::cin >> n >> m;
  14.     fact[0] = 1;
  15.     for(int i = 1;i <= n;++i){
  16.         std::cin >> a[i];
  17.         fact[i] = (fact[i - 1] * i) % M;
  18.     }
  19.     for(int i = 1;i <= m;++i){
  20.         int u,v;
  21.         std::cin >> u >> v;
  22.         adj[u].emplace_back(v);
  23.         adj[v].emplace_back(u);
  24.     }
  25. }
  26. long long f(long long t){
  27.     return t * (t - 1) / 2;
  28. }
  29. long long solve(){
  30.     long long ans = 0;
  31.     for(int i = 1;i <= n;++i){
  32.         long long t = adj[i].size();
  33.         ans = (ans + (t * f(n) % M) * a[i] % M * fact[n - 2]) % M;
  34.     }
  35.     return ans;
  36. }
  37. long long brute(){
  38.     long long ans = 0;
  39.     std::vector<int> idx(n + 1,0);
  40.     for(int i = 1;i <= n;++i){
  41.         idx[i] = i;
  42.     }
  43.     do{
  44.         std::vector<bool> vis(n + 1,0);
  45.         for(int i = 1;i <= n;++i){
  46.             int it = idx[i];
  47.             vis[it] = true;
  48.             for(int u : adj[it]){
  49.                 if(!vis[u]){
  50.                     ans += a[u];
  51.                 }
  52.                 ans %= M;
  53.             }
  54.         }
  55.     }while(std::next_permutation(idx.begin() + 1,idx.end()));
  56.     return ans;
  57. }
  58. int main(){
  59.     std::ios_base::sync_with_stdio(false);
  60.     std::cin.tie(nullptr);
  61.     freopen("order.inp","r",stdin);
  62.     freopen("order.ans","w",stdout);
  63.     readData();
  64.     std::cout << solve();
  65.     return 0;
  66. }
  67.  
Success #stdin #stdout 0.01s 10140KB
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https://ideone.com/wOIE63
language:
C++ (gcc 8.3)
created:
5 days ago
visibility:
public

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