結果

問題 No.196 典型DP (1)
コンテスト
ユーザー fumiphys
提出日時 2019-05-11 15:06:07
言語 C++14
(gcc 13.3.0 + boost 1.87.0)
結果
AC  
実行時間 47 ms / 2,000 ms
コード長 4,110 bytes
コンパイル時間 1,634 ms
コンパイル使用メモリ 173,196 KB
実行使用メモリ 58,112 KB
最終ジャッジ日時 2024-07-02 01:12:34
合計ジャッジ時間 3,708 ms
ジャッジサーバーID
（参考情報） 		judge5 / judge2
このコードへのチャレンジ
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ファイルパターン 結果
sample AC * 3
other AC * 41
権限があれば一括ダウンロードができます

ソースコード

diff # 

// includes
#include <bits/stdc++.h>

// macros
#define ll long long int
#define pb emplace_back
#define mk make_pair
#define pq priority_queue
#define FOR(i, a, b) for(int i=(a);i<(b);++i)
#define rep(i, n) FOR(i, 0, n)
#define rrep(i, n) for(int i=((int)(n)-1);i>=0;i--)
#define irep(st, itr) for(auto itr = (st).begin(); itr != (st).end(); ++itr)
#define vrep(v, i) for(int i = 0; i < (v).size(); i++)
#define all(x) (x).begin(),(x).end()
#define sz(x) ((int)(x).size())
#define UNIQUE(v) v.erase(unique(v.begin(), v.end()), v.end())
#define FI first
#define SE second
#define dump(a, n) for(int i = 0; i < n; i++)cout << a[i] << "\n "[i + 1 != n];
#define dump2(a, n, m) for(int i = 0; i < n; i++)for(int j = 0; j < m; j++)cout << a[i][j] << "\n "[j + 1 != m];
using namespace std;

//  types
typedef pair<int, int> P;
typedef pair<ll, int> Pl;
typedef pair<ll, ll> Pll;
typedef pair<double, double> Pd;
typedef complex<double> cd;
 
// constants
const int inf = 1e9;
const ll linf = 1LL << 50;
const double EPS = 1e-10;
const int mod = 1e9 + 7;

// solve
template <class T>bool chmax(T &a, const T &b){if(a < b){a = b; return 1;} return 0;}
template <class T>bool chmin(T &a, const T &b){if(a > b){a = b; return 1;} return 0;}
template <typename T> istream &operator>>(istream &is, vector<T> &vec){for(auto &v: vec)is >> v; return is;}
template <typename T> ostream &operator<<(ostream &os, const vector<T>& vec){for(int i = 0; i < vec.size(); i++){ os << vec[i]; if(i + 1 != vec.size())os << " ";} return os;}
template <typename T> ostream &operator<<(ostream &os, const set<T>& st){for(auto itr = st.begin(); itr != st.end(); ++itr){ os << *itr; auto titr = itr; if(++titr != st.end())os << " ";} return os;}
template <typename T> ostream &operator<<(ostream &os, const unordered_set<T>& st){for(auto itr = st.begin(); itr != st.end(); ++itr){ os << *itr; auto titr = itr; if(++titr != st.end())os << " ";} return os;}
template <typename T> ostream &operator<<(ostream &os, const multiset<T>& st){for(auto itr = st.begin(); itr != st.end(); ++itr){ os << *itr; auto titr = itr; if(++titr != st.end())os << " ";} return os;}
template <typename T> ostream &operator<<(ostream &os, const unordered_multiset<T>& st){for(auto itr = st.begin(); itr != st.end(); ++itr){ os << *itr; auto titr = itr; if(++titr != st.end())os << " ";} return os;}
template <typename T1, typename T2> ostream &operator<<(ostream &os, const pair<T1, T2> &p){os << p.first << " " << p.second; return os;}
template <typename T1, typename T2> ostream &operator<<(ostream &os, const map<T1, T2> &mp){for(auto itr = mp.begin(); itr != mp.end(); ++itr){ os << itr->first << ":" << itr->second; auto titr = itr; if(++titr != mp.end())os << " "; } return os;}
template <typename T1, typename T2> ostream &operator<<(ostream &os, const unordered_map<T1, T2> &mp){for(auto itr = mp.begin(); itr != mp.end(); ++itr){ os << itr->first << ":" << itr->second; auto titr = itr; if(++titr != mp.end())os << " "; } return os;}

vector<int> edge[2001];
bool vis[2001];
vector<int> child[2001];
int siz[2001];

void dfs(int i){
  siz[i] = 1;
  vis[i] = true;
  for(auto e: edge[i]){
    if(!vis[e]){
      dfs(e);
      child[i].pb(e);
      siz[i] += siz[e];
    }
  }
}

ll dp[2001][2001];
int n, k;

void calc(int i){
  int t = min(k, siz[i] - 1);
  vector<ll> d(t + 1, 0);
  vector<ll> d2(t + 1, 0);
  d[0] = 1;
  int curr = 0;
  rep(j, sz(child[i])){
    calc(child[i][j]);
    d2.assign(t + 1, 0);
    rep(l, curr+1){
      rep(m, siz[child[i][j]] + 1){
        if(l + m < t + 1){
          (d2[l+m] += d[l] * dp[child[i][j]][m] % mod) %= mod;
        }
      }
    }
    curr += siz[child[i][j]];
    swap(d, d2);
  }
  rep(l, t+1)dp[i][l] = d[l];
  dp[i][0] = 1;
  dp[i][siz[i]] = 1;
}

int main(int argc, char const* argv[])
{
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cin >> n >> k;
  rep(i, n - 1){
    int a, b;
    cin >> a >> b;
    edge[a].pb(b);
    edge[b].pb(a);
  }
  dfs(0);
  calc(0);
  // rep(i, n){
    // rep(j, k+1)cout << i << " " << j << " " << dp[i][j] << endl;
  // }
  cout << dp[0][k] << endl;
  return 0;
}
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