zoukankan      html  css  js  c++  java
  • Kolya and Tanya (次幂取模)

    Kolya and Tanya

    Time Limit:1000MS     Memory Limit:262144KB     64bit IO Format:%I64d & %I64u

    Description

    Kolya loves putting gnomes at the circle table and giving them coins, and Tanya loves studying triplets of gnomes, sitting in the vertexes of an equilateral triangle.

    More formally, there are 3n gnomes sitting in a circle. Each gnome can have from 1 to 3 coins. Let's number the places in the order they occur in the circle by numbers from 0 to 3n - 1, let the gnome sitting on the i-th place have ai coins. If there is an integer i (0 ≤ i < n) such that ai + ai + n + ai + 2n ≠ 6, then Tanya is satisfied.

    Count the number of ways to choose ai so that Tanya is satisfied. As there can be many ways of distributing coins, print the remainder of this number modulo 109 + 7. Two ways, a and b, are considered distinct if there is index i (0 ≤ i < 3n), such that ai ≠ bi (that is, some gnome got different number of coins in these two ways).

    Input

    A single line contains number n (1 ≤ n ≤ 105) — the number of the gnomes divided by three.

    Output

    Print a single number — the remainder of the number of variants of distributing coins that satisfy Tanya modulo 109 + 7.

    Sample Input

    Input
    1
    Output
    20
    Input
    2
    Output
    680

    Hint

    20 ways for n = 1 (gnome with index 0 sits on the top of the triangle, gnome 1 on the right vertex, gnome 2 on the left vertex): 

    #include <cstdio>
    typedef long long int LL;
    const LL MOD = 1000000000+7;
    LL deal_pow(LL a, LL b)
    {
        LL ans=1;
        while(b)
        {
            if(b& 1) 
                ans=(ans*a)%MOD;
            b/= 2;
            a=(a*a)%MOD;
        }
        return ans;
    }
    int main()
    {
        LL n; 
        while(scanf("%lld", &n) != EOF)
        {
            printf("%I64d
    ", (deal_pow(3, 3*n)-deal_pow(7, n)+MOD)%MOD);   //次幂取模后相减会出现负数 ; 
        }
        return 0;
    }
  • 相关阅读:
    对象之间是有联系的
    java发展历程、常用dos命令与jDK工具使用
    java环境变量、集成开发环境与使用两个类
    C++中,将单精度浮点数转换成2进制数
    Java代码规范、基本类型和实例演练
    java方法的理解、调用栈与异常处理
    java面向对象、构造方法 之内部类
    java读代码步骤
    Java中break、continue、return语句的使用区别
    数学图像处理--空间滤波
  • 原文地址:https://www.cnblogs.com/soTired/p/5446818.html
Copyright © 2011-2022 走看看