結果
問題 | No.1227 I hate ThREE |
ユーザー |
|
提出日時 | 2020-09-11 23:37:22 |
言語 | C++17 (gcc 13.3.0 + boost 1.87.0) |
結果 |
AC
|
実行時間 | 79 ms / 2,000 ms |
コード長 | 4,299 bytes |
コンパイル時間 | 2,880 ms |
コンパイル使用メモリ | 222,720 KB |
最終ジャッジ日時 | 2025-01-14 12:01:14 |
ジャッジサーバーID (参考情報) |
judge4 / judge5 |
(要ログイン)
ファイルパターン | 結果 |
---|---|
sample | AC * 3 |
other | AC * 33 |
ソースコード
#include <bits/stdc++.h>using namespace std;#define rep(i, n) for(int i = 0; i < n; i++)#define rep2(i, x, n) for(int i = x; i <= n; i++)#define rep3(i, x, n) for(int i = x; i >= n; i--)#define elif else if#define sp(x) fixed << setprecision(x)#define pb push_back#define eb emplace_back#define all(x) x.begin(), x.end()#define sz(x) (int)x.size()using ll = long long;using pii = pair<int, int>;using pil = pair<int, ll>;using pli = pair<ll, int>;using pll = pair<ll, ll>;const ll MOD = 1000000007;//const ll MOD = 998244353;const int inf = (1<<30)-1;const ll INF = (1LL<<60)-1;const double pi = acos(-1.0);const double EPS = 1e-10;template<typename T> bool chmax(T &x, const T &y) {return (x < y)? (x = y, true) : false;};template<typename T> bool chmin(T &x, const T &y) {return (x > y)? (x = y, true) : false;};template<ll mod>struct Mod_Int{ll x;Mod_Int() = default;Mod_Int(ll y) : x(y >= 0 ? y % mod : (mod - (-y) % mod) % mod) {}Mod_Int &operator += (const Mod_Int &p){x = (x + p.x) % mod;return *this;}Mod_Int &operator -= (const Mod_Int &p){x = (x + mod - p.x) % mod;return *this;}Mod_Int &operator *= (const Mod_Int &p){x = (x * p.x) % mod;return *this;}Mod_Int &operator /= (const Mod_Int &p){*this *= p.inverse();return *this;}Mod_Int &operator ++ () {return *this += Mod_Int(1);}Mod_Int operator ++ (int){Mod_Int tmp = *this;++*this;return tmp;}Mod_Int &operator -- () {return *this -= Mod_Int(1);}Mod_Int operator -- (int){Mod_Int tmp = *this;--*this;return tmp;}Mod_Int operator - () const {return Mod_Int(-x);}Mod_Int operator + (const Mod_Int &p) const {return Mod_Int(*this) += p;}Mod_Int operator - (const Mod_Int &p) const {return Mod_Int(*this) -= p;}Mod_Int operator * (const Mod_Int &p) const {return Mod_Int(*this) *= p;}Mod_Int operator / (const Mod_Int &p) const {return Mod_Int(*this) /= p;}bool operator == (const Mod_Int &p) const {return x == p.x;}bool operator != (const Mod_Int &p) const {return x != p.x;}Mod_Int inverse() const {assert(*this != Mod_Int(0));return pow(mod-2);}Mod_Int pow(ll k) const{Mod_Int now = *this, ret = 1;while(k){if(k&1) ret *= now;now *= now, k >>= 1;}return ret;}friend ostream &operator << (ostream &os, const Mod_Int &p){return os << p.x;}friend istream &operator >> (istream &is, Mod_Int &p){ll a;is >> a;p = Mod_Int<mod>(a);return is;}};using mint = Mod_Int<MOD>;struct Graph{vector<vector<int>> es;const int n;vector<vector<mint>> memo;Graph(int n) : n(n){es.resize(n);memo.assign(n, vector<mint>(n+1, -1));}void add_edge(int from, int to, bool directed = false){es[from].pb(to);if(!directed) es[to].pb(from);}mint dfs(int now, int pre, int c, int C){if(memo[now][c] != -1) return memo[now][c];mint ret = 1;for(auto &e: es[now]){if(e == pre) continue;mint tmp = 0;if(c == n){tmp += dfs(e, now, n, C)*2;}else{if(c >= 1) tmp += dfs(e, now, c-1, C);int nc = min(c+1, C-1-(c+1));if(nc >= 0) tmp += dfs(e, now, nc, C);}ret *= tmp;}return memo[now][c] = ret;}mint solve(int c){rep(i, n) rep(j, n+1) memo[i][j] = -1;mint ret = 0;if(c <= 2*n){rep(i, c){ret += dfs(0, -1, min(i, c-1-i), c);}return ret;}rep(i, n){ret += dfs(0, -1, i, c)*2;}ret += dfs(0, -1, n, c)*(c-2*n);return ret;}};int main(){int N, C;cin >> N >> C;Graph G(N);rep(i, N-1){int u, v; cin >> u >> v; u--, v--;G.add_edge(u, v);}mint ans = 0;rep(i, 3){ans += G.solve((C+i)/3);}cout << ans << endl;}