結果

問題 No.1227 I hate ThREE
ユーザー tokusakuraitokusakurai
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
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 * 33
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 #
プレゼンテーションモードにする

#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;
}
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