#344888 (Java) No.827 総神童数

• 問題: No.827 総神童数
• ユーザー: Oland
• 提出日時: 2019-05-03 23:12:52
• 言語: Java (openjdk 23)
• 結果: TLE
• 実行時間: -
• コード長: 5,357 bytes
• コンパイル時間: 2,791 ms
• コンパイル使用メモリ: 83,204 KB
• 実行使用メモリ: 163,576 KB
• 最終ジャッジ日時: 2024-12-31 19:07:31
• 合計ジャッジ時間: 88,732 ms
• ジャッジサーバーID （参考情報）: judge3 / judge4

ファイルパターン	結果
sample	AC * 3
other	AC * 9 TLE * 27

ソースコード

import java.io.*;
import java.util.*;
import java.util.Map.Entry;
import java.util.stream.Collectors;

@SuppressWarnings("unused")
public class Main {
	
	//final boolean isDebug = true;
	final boolean isDebug = false;
	String fileName = "input.txt";
	FastScanner sc;
	PrintWriter out;
	final int MOD = (int)1e9+7;
	final int INF = Integer.MAX_VALUE / 2;
	
	void solve() throws Exception{
		CombCalculator cc = new CombCalculator();
		int N = sc.nextInt();
		ArrayList<ArrayList<Integer>> G = new ArrayList<>();
		for(int i = 0; i < N; i++) G.add(new ArrayList<>());
		for(int i = 0; i < N-1; i++){
			int u = sc.nextInt()-1;
			int v = sc.nextInt()-1;
			G.get(u).add(v);
			G.get(v).add(u);
		}
		boolean[] visited = new boolean[N];
		int[] numAncestor = new int[N];
		Deque<List<Integer>> queue = new ArrayDeque<List<Integer>>();
		queue.addFirst(Arrays.asList(0, 0));
		visited[0] = true;
		
		while(queue.size() != 0){
			List<Integer> q = queue.removeFirst();
			int v = q.get(0), num = q.get(1);
			for(int next : G.get(v)){
				if(!visited[next]){
					visited[next] = true;
					numAncestor[next] = num + 1;
					queue.addFirst(Arrays.asList(next, num+1));
				}
			}
		}
		
		long ans = 0;
		for(int num : numAncestor){
			long sum = 0;
			//?
			for(int i = num; i <= N-1; i++){
				sum += cc.perm(i, num);
				sum %= MOD;
			}
			sum *= cc.fact(N-num-1);
			sum %= MOD;
			ans += sum;
			ans %= MOD;
		}
		System.out.println(ans);
	}
	
	/* end solve */
	
	/* main */
	public static void main(String[] args) throws Exception {
		new Main().m();
	}
	
	void m() throws Exception {
		long S = System.currentTimeMillis();
		sc = (isDebug) ? new FastScanner(new FileInputStream(fileName)) : new FastScanner(System.in);
		out = new PrintWriter(System.out);
		solve();
		out.flush();
		long G = System.currentTimeMillis();
		if(isDebug){
			System.out.println("---Debug---");
			System.out.printf("%8d ms", (G-S));
		}
	}
	/* end main */
}
/* end Main */

class CombCalculator{
	//MOD、階乗・MODの逆元・階乗の逆元のテーブル
	static int MAX_FAC = 510001;
	static int MOD = 1000000007;
	static long[] fac = new long[MAX_FAC];
	static long[] finv = new long[MAX_FAC];
	static long[] inv = new long[MAX_FAC];
	
	public CombCalculator(){
		initComb();
	}
	
	//テーブルの初期化
	void initComb(){
		fac[0] = finv[0] = inv[0] = fac[1] = finv[1] = inv[1] = 1;
		for (int i = 2; i < MAX_FAC; ++i) {
			fac[i] = fac[i - 1] * i % MOD;
			inv[i] = MOD - (MOD / i) * inv[(int) (MOD % i)] % MOD;
			finv[i] = finv[i - 1] * inv[i] % MOD;
		}
	}
	
	//nPk % MOD
	public long perm(int n, int k){
		return fac[n] * finv[n - k] % MOD;
	}
	
	//nCk % MOD
	public long comb(int n, int k){
		return fac[n] * finv[k] % MOD * finv[n - k] % MOD;
	}
	
	//n! % MOD
	public long fact(int n){
		return fac[n];
	}
	
	//(n!)^-1 % MOD
	public long finv(int n){
		return finv[n];
	}
}

class FastScanner {
    private InputStream in;
    private final byte[] buffer = new byte[1024];
    private int ptr = 0;
    private int buflen = 0;
    public FastScanner(InputStream in) {
		this.in = in;
	}
    private boolean hasNextByte() {
        if (ptr < buflen) {
            return true;
        }else{
            ptr = 0;
            try {
                buflen = in.read(buffer);
            } catch (IOException e) {
                e.printStackTrace();
            }
            if (buflen <= 0) {
                return false;
            }
        }
        return true;
    }
    private int readByte() {
    	if (hasNextByte()) return buffer[ptr++];
    	else return -1;
    }
    private static boolean isPrintableChar(int c){
    	return 33 <= c && c <= 126;
    }
    public boolean hasNext() {
    	while(hasNextByte() && !isPrintableChar(buffer[ptr]))
    		ptr++; return hasNextByte();
    }
    public String next() {
        if (!hasNext()) throw new NoSuchElementException();
        StringBuilder sb = new StringBuilder();
        int b = readByte();
        while(isPrintableChar(b)) {
            sb.appendCodePoint(b);
            b = readByte();
        }
        return sb.toString();
    }
    public String nextLine() {
        if (!hasNext()) throw new NoSuchElementException();
        StringBuilder sb = new StringBuilder();
        int b = readByte();
        while(b != 10) {
            sb.appendCodePoint(b);
            b = readByte();
        }
        return sb.toString();
    }
    public long nextLong() {
        if (!hasNext()) throw new NoSuchElementException();
        long n = 0;
        boolean minus = false;
        int b = readByte();
        if (b == '-') {
            minus = true;
            b = readByte();
        }
        if (b < '0' || '9' < b) {
            throw new NumberFormatException();
        }
        while(true){
            if ('0' <= b && b <= '9') {
                n *= 10;
                n += b - '0';
            }else if(b == -1 || !isPrintableChar(b)){
                return minus ? -n : n;
            }else{
                throw new NumberFormatException();
            }
            b = readByte();
        }
    }
    public int nextInt() {
        long nl = nextLong();
        if (nl < Integer.MIN_VALUE || nl > Integer.MAX_VALUE) throw new NumberFormatException();
        return (int) nl;
    }
    public double nextDouble() {
    	return Double.parseDouble(next());
    }
}