結果
問題 | No.758 VVVVV |
ユーザー |
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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 |
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ファイルパターン | 結果 |
---|---|
sample | AC * 3 |
other | AC * 23 |
ソースコード
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)); } }