結果

問題 No.758 VVVVV
ユーザー 👑 hos.lyric
提出日時 2019-04-05 07:38:26
言語 D
(dmd 2.109.1)
結果
AC  
実行時間 118 ms / 2,000 ms
コード長 3,103 bytes
コンパイル時間 1,066 ms
コンパイル使用メモリ 121,960 KB
実行使用メモリ 25,104 KB
最終ジャッジ日時 2024-06-13 04:49:49
合計ジャッジ時間 3,760 ms
ジャッジサーバーID
(参考情報)
judge1 / judge5
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

import std.conv, std.functional, std.stdio, std.string;
import std.algorithm, std.array, std.bigint, std.container, std.math, std.numeric, std.range, std.regex, std.typecons;
import core.bitop;
class EOFException : Throwable { this() { super("EOF"); } }
string[] tokens;
string readToken() { for (; tokens.empty; ) { if (stdin.eof) { throw new EOFException; } tokens = readln.split; } auto token = tokens.front; tokens
    .popFront; return token; }
int readInt() { return readToken.to!int; }
long readLong() { return readToken.to!long; }
real readReal() { return readToken.to!real; }
bool chmin(T)(ref T t, in T f) { if (t > f) { t = f; return true; } else { return false; } }
bool chmax(T)(ref T t, in T f) { if (t < f) { t = f; return true; } else { return false; } }
int binarySearch(alias pred, T)(in T[] as) { int lo = -1, hi = cast(int)(as.length); for (; lo + 1 < hi; ) { const mid = (lo + hi) >> 1;
    (unaryFun!pred(as[mid]) ? hi : lo) = mid; } return hi; }
int lowerBound(T)(in T[] as, T val) { return as.binarySearch!(a => (a >= val)); }
int upperBound(T)(in T[] as, T val) { return as.binarySearch!(a => (a > val)); }
enum MO = 10L^^9 + 7;
enum LIM = 3 * 10^^5;
long[] inv, fac, invFac;
void prepare() {
inv = new long[LIM];
fac = new long[LIM];
invFac = new long[LIM];
inv[1] = 1;
foreach (i; 2 .. LIM) {
inv[i] = MO - ((MO / i) * inv[cast(size_t)(MO % i)]) % MO;
}
fac[0] = invFac[0] = 1;
foreach (i; 1 .. LIM) {
fac[i] = (fac[i - 1] * i) % MO;
invFac[i] = (invFac[i - 1] * inv[i]) % MO;
}
}
long binom(long n, long k) {
if (0 <= k && k <= n) {
assert(n < LIM);
return fac[cast(size_t)(n)] * invFac[cast(size_t)(k)] % MO * invFac[cast(size_t)(n - k)] % MO;
} else {
return 0;
}
}
int N;
int[] A, B;
int[][] G;
int cntLeaf;
void dfs(int u, int p) {
bool isLeaf = true;
foreach (v; G[u]) {
if (v != p) {
isLeaf = false;
dfs(v, u);
}
}
if (isLeaf) {
++cntLeaf;
}
}
void main() {
prepare();
debug {
enum lim = 10;
auto dp = new long[][][](lim, lim, lim);
foreach (a; 1 .. lim) foreach (b; 1 .. lim) {
dp[a][b][1] = 1;
foreach (k; 2 .. lim) {
foreach (aa; 1 .. a) foreach (bb; 1 .. b) {
if (aa >= bb) {
dp[a][b][k] += dp[aa][bb][k - 1];
}
}
}
}
foreach (n; 1 .. lim) {
foreach (k; 1 .. lim) {
write(" ", dp[n][n][k]);
}
writeln();
}
}
try {
for (; ; ) {
N = readInt();
A = new int[N - 1];
B = new int[N - 1];
foreach (i; 0 .. N - 1) {
A[i] = readInt() - 1;
B[i] = readInt() - 1;
}
G = new int[][N];
foreach (i; 0 .. N - 1) {
G[A[i]] ~= B[i];
G[B[i]] ~= A[i];
}
cntLeaf = 0;
dfs(0, -1);
long ans = 1;
if (N > 1) {
ans *= binom(N - 1 - 1, cntLeaf - 1);
ans %= MO;
ans *= binom(N - 1, cntLeaf - 1);
ans %= MO;
ans *= inv[cntLeaf];
ans %= MO;
}
writeln(ans);
}
} catch (EOFException e) {
}
}
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