結果

問題 No.196 典型DP (1)
ユーザー HaarHaar
提出日時 2019-08-07 04:34:34
言語 C++17
(gcc 13.3.0 + boost 1.87.0)
結果
AC  
実行時間 50 ms / 2,000 ms
コード長 3,326 bytes
コンパイル時間 2,350 ms
コンパイル使用メモリ 199,864 KB
最終ジャッジ日時 2025-01-07 10:56:36
ジャッジサーバーID
（参考情報） 		judge5 / judge1
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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 # 

#include <bits/stdc++.h>
#define LLI long long int
#define FOR(v, a, b) for(LLI v = (a); v < (b); ++v)
#define FORE(v, a, b) for(LLI v = (a); v <= (b); ++v)
#define REP(v, n) FOR(v, 0, n)
#define REPE(v, n) FORE(v, 0, n)
#define REV(v, a, b) for(LLI v = (a); v >= (b); --v)
#define ALL(x) (x).begin(), (x).end()
#define RALL(x) (x).rbegin(), (x).rend()
#define ITR(it, c) for(auto it = (c).begin(); it != (c).end(); ++it)
#define RITR(it, c) for(auto it = (c).rbegin(); it != (c).rend(); ++it)
#define EXIST(c,x) ((c).find(x) != (c).end())
#define fst first
#define snd second
#define popcount __builtin_popcount
#define UNIQ(v) (v).erase(unique(ALL(v)), (v).end())
#define bit(i) (1LL<<(i))

#ifdef DEBUG
#include <misc/C++/Debug.cpp>
#else
#define dump(...) ((void)0)
#endif

#define gcd __gcd

using namespace std;
template <class T> constexpr T lcm(T m, T n){return m/gcd(m,n)*n;}

template <typename I> void join(ostream &ost, I s, I t, string d=" "){for(auto i=s; i!=t; ++i){if(i!=s)ost<<d; ost<<*i;}ost<<endl;}
template <typename T> istream& operator>>(istream &is, vector<T> &v){for(auto &a : v) is >> a; return is;}

template <typename T, typename U> bool chmin(T &a, const U &b){return (a>b ? a=b, true : false);}
template <typename T, typename U> bool chmax(T &a, const U &b){return (a<b ? a=b, true : false);}
template <typename T, size_t N, typename U> void fill_array(T (&a)[N], const U &v){fill((U*)a, (U*)(a+N), v);}

template <typename Cost = int> class Edge{
public:
  int from,to;
  Cost cost;
  Edge() {}
  Edge(int to, Cost cost): to(to), cost(cost){}
  Edge(int from, int to, Cost cost): from(from), to(to), cost(cost){}

  Edge rev() const {return Edge(to,from,cost);}
  
  friend ostream& operator<<(ostream &os, const Edge &e){
    os << "(FROM: " << e.from << "," << "TO: " << e.to << "," << "COST: " << e.cost << ")";
    return os;
  }
};

template <typename T> using Graph = vector<vector<Edge<T>>>;
template <typename T> using Tree = vector<vector<Edge<T>>>;

template <typename C, typename T> void add_edge(C &g, int from, int to, T w){
  g[from].push_back(Edge<T>(from, to, w));  
}

template <typename C, typename T> void add_undirected(C &g, int a, int b, T w){
  g[a].push_back(Edge<T>(a, b, w));
  g[b].push_back(Edge<T>(b, a, w));
}


const LLI mod = 1e9+7;

LLI dp[2200][2200][2];
LLI dp2[2200][2];
int subtree[2200];

Tree<int> tree;

int n,k;


void rec(int cur, int par){
  subtree[cur] = 1;
  
  for(auto &e : tree[cur]){
    if(e.to == par) continue;
    rec(e.to, cur);
    subtree[cur] += subtree[e.to];
  }

  fill_array(dp2, 0);


  dp[cur][0][0] = 1;
  dp[cur][subtree[cur]][1] = 1;

  int s = 0;

  for(auto &e : tree[cur]){
    if(e.to == par) continue;

    FORE(i,0,s){
      FORE(j,0,subtree[e.to]){
        (dp2[i+j][0] += dp[cur][i][0] * (dp[e.to][j][0]+dp[e.to][j][1]) % mod) %= mod;
      }
    }

    s += subtree[e.to];

    FORE(i,0,k){
      dp[cur][i][0] = dp2[i][0];
      dp2[i][0] = 0;
    }
  }
}


int main(){
  cin.tie(0);
  ios::sync_with_stdio(false);

  while(cin >> n >> k){
    tree = Tree<int>(n);
    REP(i,n-1){
      int u,v; cin >> u >> v;
      add_undirected(tree,u,v,1);
    }

    fill_array(dp, 0);
    fill_array(subtree, 0);

    rec(0,-1);
    
    LLI ans = (dp[0][k][0] + dp[0][k][1]) % mod;
    cout << ans << endl;
  }
  
  return 0;
}
0