結果

問題 No.758 VVVVV
ユーザー paruki
提出日時 2018-12-19 08:52:39
言語 C++14
(gcc 13.3.0 + boost 1.87.0)
結果
AC  
実行時間 51 ms / 2,000 ms
コード長 3,393 bytes
コンパイル時間 1,815 ms
コンパイル使用メモリ 169,952 KB
実行使用メモリ 5,248 KB
最終ジャッジ日時 2024-10-14 01:50:20
合計ジャッジ時間 3,780 ms
ジャッジサーバーID
(参考情報)
judge3 / judge4
このコードへのチャレンジ
(要ログイン)
ファイルパターン 結果
sample AC * 3
other AC * 23
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

#define _USE_MATH_DEFINES
#include "bits/stdc++.h"
using namespace std;
#define FOR(i,j,k) for(int (i)=(j);(i)<(int)(k);++(i))
#define rep(i,j) FOR(i,0,j)
#define each(x,y) for(auto &(x):(y))
#define mp make_pair
#define MT make_tuple
#define all(x) (x).begin(),(x).end()
#define debug(x) cout<<#x<<": "<<(x)<<endl
#define smax(x,y) (x)=max((x),(y))
#define smin(x,y) (x)=min((x),(y))
#define MEM(x,y) memset((x),(y),sizeof (x))
#define sz(x) (int)(x).size()
#define RT return
using ll = long long;
using pii = pair<int, int>;
using vi = vector<int>;
using vll = vector<ll>;
template<int MOD>
class ModInt {
public:
ModInt() :value(0) {}
ModInt(long long val) :value((int)(val<0 ? MOD + val % MOD : val % MOD)) { }
ModInt& operator+=(ModInt that) {
value = value + that.value;
if (value >= MOD)value -= MOD;
return *this;
}
ModInt& operator-=(ModInt that) {
value -= that.value;
if (value<0)value += MOD;
return *this;
}
ModInt& operator*=(ModInt that) {
value = (int)((long long)value * that.value % MOD);
return *this;
}
ModInt &operator/=(ModInt that) {
return *this *= that.inverse();
}
ModInt operator+(ModInt that) const {
return ModInt(*this) += that;
}
ModInt operator-(ModInt that) const {
return ModInt(*this) -= that;
}
ModInt operator*(ModInt that) const {
return ModInt(*this) *= that;
}
ModInt operator/(ModInt that) const {
return ModInt(*this) /= that;
}
ModInt pow(long long k) const {
ModInt n = *this, res = 1;
while (k) {
if (k & 1)res *= n;
n *= n;
k >>= 1;
}
return res;
}
ModInt inverse() const {
long long a = value, b = MOD, u = 1, v = 0;
while (b) {
long long t = a / b;
a -= t * b;
swap(a, b);
u -= t * v;
swap(u, v);
}
return ModInt(u);
}
int toi() const { return value; }
private:
int value;
};
typedef ModInt<1000000007> mint;
ostream& operator<<(ostream& os, const mint& x) {
os << x.toi();
return os;
}
namespace comb {
const int N = 100005;
mint fact[N];
mint rev[N];
void init() {
fact[0] = 1;
for (int i = 1; i < N; ++i)fact[i] = fact[i - 1] * i;
for (int i = 0; i < N; ++i)rev[i] = fact[i].inverse();
}
mint C(int n, int r) {
if (n < r)return 0;
return fact[n] * rev[r] * rev[n - r];
}
mint H(int n, int r) {
return C(n + r - 1, r);
}
mint P(int n, int r) {
assert(n >= r);
return fact[n] * rev[n - r];
}
mint catalan(int n) {
return fact[2 * n] * rev[n + 1] * rev[n];
}
}
mint narayana(int m, int l) {
return comb::C(m, l - 1)*comb::C(m - 1, l - 1) / l;
}
void solve() {
comb::init();
int N;
cin >> N;
vi deg(N);
rep(i, N-1) {
int u, v;
cin >> u >> v;
deg[u - 1]++;
deg[v - 1]++;
}
if (N == 1) {
cout << 1 << endl;
return;
}
int leaves = 0;
FOR(i, 1, N) {
if (deg[i] == 1)leaves++;
}
cout << narayana(N - 1, leaves) << endl;
}
int main() {
ios::sync_with_stdio(false);
cin.tie(0);
cout << fixed << setprecision(15);
solve();
return 0;
}
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