結果

問題 No.391 CODING WAR
コンテスト
ユーザー hiromi_ayase
提出日時 2016-07-08 23:22:44
言語 Java
(openjdk 23)
結果
TLE  
実行時間 -
コード長 3,946 bytes
コンパイル時間 2,064 ms
コンパイル使用メモリ 77,608 KB
実行使用メモリ 60,980 KB
最終ジャッジ日時 2024-10-13 07:04:46
合計ジャッジ時間 6,435 ms
ジャッジサーバーID
（参考情報） 		judge4 / judge3
このコードへのチャレンジ
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ファイルパターン 結果
sample AC * 4
other AC * 5 TLE * 1 -- * 10
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 # 

import java.io.IOException;
import java.io.InputStream;
import java.util.NoSuchElementException;

public class Main {
	private static long mod = 1000000007;

	public static void main(String[] args) {
		FastScanner sc = new FastScanner();
		long N = sc.nextLong();
		long M = sc.nextLong();

		long ret = 0;
		for (int m = 0; m < M; m++) {
			long x = powMod(M - m, N);
			long y = combMod(M, m);
			long s = m % 2 == 0 ? 1 : -1;

			ret += s * x * y;
			ret = (ret + mod) % mod;
		}
		System.out.println(ret);
	}

	public static long combMod(long n, long r) {
		long comb = 1;
		for (int i = 0; i < r; i++) {
			comb = (comb * (n - i)) % mod;
			comb = (comb * inverse(r - i, mod)) % mod;
		}
		return comb;
	}

	public static long[] extgcd(long a, long b) {
		long u = 1;
		long v = 0;
		long x = 0;
		long y = 1;

		while (a > 0) {
			long q = b / a;
			x -= q * u;
			y -= q * v;
			b -= q * a;

			long tmp;
			tmp = x;
			x = u;
			u = tmp;
			tmp = y;
			y = v;
			v = tmp;
			tmp = b;
			b = a;
			a = tmp;
		}

		return new long[] { b, x, y };
	}

	public static long inverse(long n, long mod) {
		long[] gcd = extgcd(n, mod);
		if (gcd[0] == 1) {
			return (gcd[1] + mod) % mod;
		} else {
			return 0;
		}
	}

	public static long powMod(long x, long k) {
		int n = 63 - Long.numberOfLeadingZeros(k);
		long answer = 1;
		for (int i = n; i >= 0; i--) {
			answer = (answer * answer) % mod;
			if (((k >> i) & 1L) == 1L) {
				answer = (answer * x) % mod;
			}
		}
		return answer;
	}
}

class FastScanner {
	public static String debug = null;

	private final InputStream in = System.in;
	private int ptr = 0;
	private int buflen = 0;
	private byte[] buffer = new byte[1024];
	private boolean eos = false;

	private boolean hasNextByte() {
		if (ptr < buflen) {
			return true;
		} else {
			ptr = 0;
			try {
				if (debug != null) {
					buflen = debug.length();
					buffer = debug.getBytes();
					debug = "";
					eos = true;
				} else {
					buflen = in.read(buffer);
				}
			} catch (IOException e) {
				e.printStackTrace();
			}
			if (buflen < 0) {
				eos = true;
				return false;
			} else 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;
	}

	private void skipUnprintable() {
		while (hasNextByte() && !isPrintableChar(buffer[ptr]))
			ptr++;
	}

	public boolean isEOS() {
		return this.eos;
	}

	public boolean hasNext() {
		skipUnprintable();
		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 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() {
		return (int) nextLong();
	}

	public long[] nextLongList(int n) {
		return nextLongTable(1, n)[0];
	}

	public int[] nextIntList(int n) {
		return nextIntTable(1, n)[0];
	}

	public long[][] nextLongTable(int n, int m) {
		long[][] ret = new long[n][m];
		for (int i = 0; i < n; i++) {
			for (int j = 0; j < m; j++) {
				ret[i][j] = nextLong();
			}
		}
		return ret;
	}

	public int[][] nextIntTable(int n, int m) {
		int[][] ret = new int[n][m];
		for (int i = 0; i < n; i++) {
			for (int j = 0; j < m; j++) {
				ret[i][j] = nextInt();
			}
		}
		return ret;
	}
}
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