Submission #1171184

#	Time	Username	Problem	Language	Result	Execution time	Memory
1171184		Zero_OP	Star Trek (CEOI20_startrek)	C++20	15 / 100	26 ms	4940 KiB

startrek

#include <bits/stdc++.h>

using namespace std;

#define FOR(i, l, r) for(int i = (l); i < (r); ++i)
#define ROF(i, r, l) for(int i = (r)-1; i >= (l); --i)

#define mp make_pair
#define mt make_tuple
#define ff first
#define ss second

#define all(v) begin(v), end(v)
#define rall(v) rbegin(v), rend(v)
#define sz(v) (int)v.size()
#define pb push_back
#define eb emplace_back
#define compact(v) v.erase(unique(all(v)), end(v))

#define dbg(x) "[" #x " = " << (x) << "]"

template<typename T>
      bool minimize(T& a, const T& b){
            if(a > b) return a = b, true;
            return false;
      }

template<typename T>
      bool maximize(T& a, const T& b){
            if(a < b) return a = b, true;
            return false;
      }

typedef long long ll;

using db = double;
using ull = unsigned long long;

using pi = pair<int, int>;
using pl = pair<ll, ll>;
using pd = pair<db, db>;

using vi = vector<int>;
using vl = vector<ll>;
using vc = vector<char>;
using vd = vector<db>;
using vb = vector<bool>;

using vpi = vector<pi>;
using vpl = vector<pl>;

void setIO(){
      ios_base::sync_with_stdio(0); cin.tie(0);
#ifdef LOCAL
      freopen("task.inp", "r", stdin);
      freopen("task.out", "w", stdout);
#endif
}

const int MAX = 1e5 + 5;
const int mod = 1e9 + 7;

struct mint{
      int v;
      mint(int v) : v(v) {}

      mint& operator += (const mint& o){
            v += o.v;
            if(v >= mod) v -= mod;
            return *this;
      }

      mint& operator -= (const mint& o){
            v -= o.v;
            if(v < 0) v += mod;
            return *this;
      }

      mint& operator *= (const mint& o){
            v = 1LL * v * o.v % mod;
            return *this;
      }

      mint power(ll n) const {
            mint res(1), base = *this;
            for(; n > 0; n >>= 1, base *= base) if(n & 1) res *= base;
            return res;
      }

      mint inv() const {
            return power(mod - 2);
      }

      mint& operator /= (const mint& o){
            return *this *= o.inv();
      }

      friend mint operator + (mint a, const mint& b){ return a += b; }
      friend mint operator - (mint a, const mint& b){ return a -= b; }
      friend mint operator * (mint a, const mint& b){ return a *= b; }
      friend mint operator / (mint a, const mint& b){ return a /= b; }

      friend ostream& operator << (ostream& out, const mint& o){ return out << o.v; }
};

int N;
ll D;
vi adj[MAX * 2];

namespace subtask2{
      bool dp[MAX * 2];

      void dfs(int u, int p){
            dp[u] = false;
            for(auto v : adj[u]) if(v != p){
                  dfs(v, u);
                  if(!dp[v]) dp[u] = 1;
            }
      }

      bool check(){
            dfs(0, -1);
            return dp[0];
      }

      void solve(){
            FOR(i, 0, N){
                  for(auto j : adj[i]) adj[i+N].pb(j+N);
            }

            int ans = 0;
            FOR(i, 0, N){
                  FOR(j, 0, N){
                        adj[i].pb(j+N);
//                        cout << dbg(i) << dbg(j+N) << '\n';
                        ans += check();
                        adj[i].pop_back();
                  }
            }
            cout << ans << '\n';
      }
}

int main(){
      setIO();

      cin >> N >> D;
      FOR(i, 0, N-1){
            int u, v;
            cin >> u >> v;
            --u, --v;
            adj[u].pb(v);
            adj[v].pb(u);
      }

      if(N == 2){
            cout << mint(4).power(D) << '\n';
            return 0;
      }

      if(N <= 100 && D == 1){
            return subtask2::solve(), 0;
      }

      return 0;
}

• Subtask 1: 0 / 0
• Subtask 2: 7 / 7
• Subtask 3: 8 / 8
• Subtask 4: 0 / 15
• Subtask 5: 0 / 15
• Subtask 6: 0 / 20
• Subtask 7: 0 / 20
• Subtask 8: 0 / 15