結果

問題 No.758 VVVVV
ユーザー hiromi_ayase
提出日時 2018-12-07 13:50:53
言語 Java
(openjdk 23)
結果
AC  
実行時間 285 ms / 2,000 ms
コード長 3,417 bytes
コンパイル時間 2,385 ms
コンパイル使用メモリ 86,040 KB
実行使用メモリ 47,696 KB
最終ジャッジ日時 2024-10-14 01:46:33
合計ジャッジ時間 8,150 ms
ジャッジサーバーID
(参考情報)
judge3 / judge2
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

public class Main {
private static void solve() {
int n = ni();
if (n == 1) {
System.out.println(1);
return;
}
int[] cnt = new int[n];
for (int i = 0; i < n-1; i ++) {
cnt[ni() - 1] ++;
cnt[ni() - 1] ++;
}
int leaf = 0;
for (int i = 1; i < n; i ++) {
if (cnt[i] == 1) leaf ++;
}
int mod = 1000000000 + 7;
long ret = c(n - 1, leaf - 1, mod) * c(n - 2, leaf - 1, mod) % mod;
ret = ret * invl(leaf, mod) % mod;
System.out.println(ret);
}
private static long c(int n, int r, int mod) {
long x = 1;
long y = 1;
for (int i = 0; i < r; i ++) {
x *= n - i;
y *= i + 1;
x %= mod;
y %= mod;
}
return x * invl(y, mod) % mod;
}
public static long invl(long a, long mod) {
long b = mod;
long p = 1, q = 0;
while (b > 0) {
long c = a / b;
long d;
d = a;
a = b;
b = d % b;
d = p;
p = q;
q = d - c * q;
}
return p < 0 ? p + mod : p;
}
public static void main(String[] args) {
new Thread(null, new Runnable() {
@Override
public void run() {
long start = System.currentTimeMillis();
String debug = args.length > 0 ? args[0] : null;
if (debug != null) {
try {
is = java.nio.file.Files.newInputStream(java.nio.file.Paths.get(debug));
} catch (Exception e) {
throw new RuntimeException(e);
}
}
reader = new java.io.BufferedReader(new java.io.InputStreamReader(is), 32768);
solve();
out.flush();
tr((System.currentTimeMillis() - start) + "ms");
}
}, "", 64000000).start();
}
private static java.io.InputStream is = System.in;
private static java.io.PrintWriter out = new java.io.PrintWriter(System.out);
private static java.util.StringTokenizer tokenizer = null;
private static java.io.BufferedReader reader;
public static String next() {
while (tokenizer == null || !tokenizer.hasMoreTokens()) {
try {
tokenizer = new java.util.StringTokenizer(reader.readLine());
} catch (Exception e) {
throw new RuntimeException(e);
}
}
return tokenizer.nextToken();
}
private static double nd() {
return Double.parseDouble(next());
}
private static long nl() {
return Long.parseLong(next());
}
private static int[] na(int n) {
int[] a = new int[n];
for (int i = 0; i < n; i++)
a[i] = ni();
return a;
}
private static char[] ns() {
return next().toCharArray();
}
private static long[] nal(int n) {
long[] a = new long[n];
for (int i = 0; i < n; i++)
a[i] = nl();
return a;
}
private static int[][] ntable(int n, int m) {
int[][] table = new int[n][m];
for (int i = 0; i < n; i++) {
for (int j = 0; j < m; j++) {
table[i][j] = ni();
}
}
return table;
}
private static int[][] nlist(int n, int m) {
int[][] table = new int[m][n];
for (int i = 0; i < n; i++) {
for (int j = 0; j < m; j++) {
table[j][i] = ni();
}
}
return table;
}
private static int ni() {
return Integer.parseInt(next());
}
private static void tr(Object... o) {
if (is != System.in)
System.out.println(java.util.Arrays.deepToString(o));
}
}
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