結果

問題 No.1518 Simple Combinatorics
コンテスト
ユーザー shojin_pro
提出日時 2021-05-28 22:55:38
言語 Java
(openjdk 23)
結果
AC  
実行時間 54 ms / 2,000 ms
コード長 4,785 bytes
コンパイル時間 2,389 ms
コンパイル使用メモリ 78,740 KB
実行使用メモリ 37,324 KB
最終ジャッジ日時 2024-11-07 10:15:20
合計ジャッジ時間 4,439 ms
ジャッジサーバーID
（参考情報） 		judge4 / judge5
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 * 3
other AC * 19
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.util.*;
import java.io.*;

public class Main {
    static FastScanner sc = new FastScanner(System.in);
    static PrintWriter pw = new PrintWriter(System.out);
    static StringBuilder sb = new StringBuilder();
    static long mod = (long) 1e9 + 7;
    public static void main(String[] args) throws Exception {
        solve();
        pw.flush();
    }
    
    public static void solve() {
        int N = sc.nextInt();
        int K = sc.nextInt();
        long rem = rep2(N,K,mod)-rep2(N-1,K,mod);
        if(rem < 0) rem += mod;
        rem *= N;
        pw.println(rem % mod);
    }
    
    private static long rep2(long b, long n, long mod){
        if(n == 0) return 1;
        long bn = rep2(b,n/2,mod);
        if(n % 2 == 0){
            return (bn*bn)%mod;
        }else{
            return (bn*bn)%mod*b%mod;
        }
    }

    static class GeekInteger {
        public static void save_sort(int[] array) {
            shuffle(array);
            Arrays.sort(array);
        }

        public static int[] shuffle(int[] array) {
            int n = array.length;
            Random random = new Random();
            for (int i = 0, j; i < n; i++) {
                j = i + random.nextInt(n - i);
                int randomElement = array[j];
                array[j] = array[i];
                array[i] = randomElement;
            }
            return array;
        }

        public static void save_sort(long[] array) {
            shuffle(array);
            Arrays.sort(array);
        }

        public static long[] shuffle(long[] array) {
            int n = array.length;
            Random random = new Random();
            for (int i = 0, j; i < n; i++) {
                j = i + random.nextInt(n - i);
                long randomElement = array[j];
                array[j] = array[i];
                array[i] = randomElement;
            }
            return array;
        }

    }
}

class Combination {
    final static long mod = (long) 1e9 + 7;
    private static long[] fact, ifact;

    public Combination(int n) {
        fact = new long[n + 1];
        ifact = new long[n + 1];
        fact[0] = 1;
        long ln = n;
        for (long i = 1; i <= ln; ++i) {
            int ii = (int) i;
            fact[ii] = fact[ii - 1] % mod * i % mod;
        }
        ifact[n] = pow(fact[n], this.mod - 2);
        for (int i = n; i >= 1; --i) {
            int ii = (int) i;
            ifact[ii - 1] = ifact[ii] % mod * i % mod;
        }
    }

    public static long comb(int n, int k) {
        if (k < 0 || k > n)
            return 0;
        return fact[n] % mod * ifact[k] % mod * ifact[n - k] % mod;
    }

    public static long perm(int n, int k) {
        return comb(n, k) * fact[k] % mod;
    }

    public static long pow(long a, long b) {
        long ret = 1;
        long tmp = a;
        while (b > 0) {
            if ((b & 1) == 1) {
                ret = (ret * tmp) % mod;
            }
            tmp = (tmp * tmp) % mod;
            b = b >> 1;
        }
        return ret;
    }
}

class FastScanner {
    private BufferedReader reader = null;
    private StringTokenizer tokenizer = null;

    public FastScanner(InputStream in) {
        reader = new BufferedReader(new InputStreamReader(in));
        tokenizer = null;
    }

    public FastScanner(FileReader in) {
        reader = new BufferedReader(in);
        tokenizer = null;
    }

    public String next() {
        if (tokenizer == null || !tokenizer.hasMoreTokens()) {
            try {
                tokenizer = new StringTokenizer(reader.readLine());
            } catch (IOException e) {
                throw new RuntimeException(e);
            }
        }
        return tokenizer.nextToken();
    }

    public String nextLine() {
        if (tokenizer == null || !tokenizer.hasMoreTokens()) {
            try {
                return reader.readLine();
            } catch (IOException e) {
                throw new RuntimeException(e);
            }
        }
        return tokenizer.nextToken("\n");
    }

    public long nextLong() {
        return Long.parseLong(next());
    }

    public int nextInt() {
        return Integer.parseInt(next());
    }

    public double nextDouble() {
        return Double.parseDouble(next());
    }

    public String[] nextArray(int n) {
        String[] a = new String[n];
        for (int i = 0; i < n; i++)
            a[i] = next();
        return a;
    }

    public int[] nextIntArray(int n) {
        int[] a = new int[n];
        for (int i = 0; i < n; i++)
            a[i] = nextInt();
        return a;
    }

    public long[] nextLongArray(int n) {
        long[] a = new long[n];
        for (int i = 0; i < n; i++)
            a[i] = nextLong();
        return a;
    }
}
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