JZOJ 4742. 单峰

Description

Input

Output

Sample Input

Sample Output

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。

 1 #include <cstdio>
 2 #include <cmath>
 3 #include <iostream>
 4 #include <cstring>
 5 #define LL long long
 6 #define mo 1000000007
 7 using namespace std;
 8 LL a,base,p;
 9 LL n;
10 
11 inline LL power(LL b){
12     a=2;
13     base=a;
14     p=1;
15     for(;b;b>>=1){
16         if(b&1) p=p*a%mo;
17         a=a*a%mo;
18     }
19     return p;
20 }
21 
22 int main(){
23     scanf("%lld",&n);
24     printf("%lld", power(n-1));
25 }

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