2017 Multi-University Training Contest

Funny Function

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 1109    Accepted Submission(s): 527

Sample Input

2

2 2

3 3

Sample Output

2 33

Source

2017 Multi-University Training Contest - Team 2

 

生病了  找时间来解释

#include<iostream>
#include<cstdio>
#include<algorithm>
#include<cstring>
#include<cstdlib>
#include<string.h>
#include<set>
#include<vector>
#include<queue>
#include<stack>
#include<map>
#include<cmath>
typedef long long ll;
typedef unsigned long long LL;
using namespace std;
const double PI=acos(-1.0);
const double eps=0.0000000001;
const int maxn=1000+10;
const int mod=1e9+7;
int pow_mod(ll a,ll b)
{
    ll ans=1;
    while(b)
    {
        if(b&1)ans=(ans*a)%mod;
        a=(a*a)%mod;
        b>>=1;
    }
    return ans;
}
int main() 
{
    int t;
    ll n,m;
    scanf("%d",&t);
    while(t--)
    {
        int x,y,ans;
        scanf("%lld%lld",&n,&m);
        if(m==1)printf("1
");
        else
        {
            x=pow_mod(3,mod-2);
            //printf("%d
",x);
            y=(pow_mod(2,n)-1+mod)%mod;
            y=pow_mod(y,m-1);
            ans =(1ll*x*y*2)%mod;
            if(n%2)
            ans=(ans+x)%mod;
        }
        printf("%d
",ans);
    }
    return 0;
}