JZOJ 4742. 单峰

Description

Input

Output

Sample Input

2

Sample Output

2

Data Constraint

做法：打标可以发现这道题是结论题，答案为2^(n-1)，所以快速幂就好了。

#include <cstdio>
#include <cmath>
#include <iostream>
#include <cstring>
#define LL long long
#define mo 1000000007
using namespace std;
LL a,base,p;
LL n;

inline LL power(LL b){
    a=2;
    base=a;
    p=1;
    for(;b;b>>=1){
        if(b&1) p=p*a%mo;
        a=a*a%mo;
    }
    return p;
}

int main(){
    scanf("%lld",&n);
    printf("%lld", power(n-1));
}