HDU4602+推导公式

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 /*
 推导公式
 a[n] = 2^(n-1) + (n-2)*2^(n-3)
 */
 #include<stdio.h>
 #include<math.h>
 #include<algorithm>
 using namespace std;
 typedef long long int64;
 const int64 mod = 1e9+;

 int64 FastPow( int64 n,int64 m ){//n^m
     int64 sum = ;
     while( m>= ){
         if( m%== ){
             sum *= n;
             sum %= mod;
         }
         n *= n;
         n %= mod;
         m/=;
     }
     return sum;
 }

 int main(){
     int T;
     scanf("%d",&T);
     while( T-- ){
         int64 n,k;
         //scanf("%lld%lld",&n,&k);
         scanf("%I64d%I64d",&n,&k);
         if( k>n ){
             printf("0\n");
             continue;
         }
         if( k==n ){
             printf("1\n");
             continue;
         }
         int64 delta = k-;
         int64 Index = n-delta;

         if( Index== ){
             printf("1\n");
             continue;
         }
         if( Index== ){
             printf("2\n");
             continue;
         }

         //printf("%lld\n",(FastPow2(2,Index-1)%mod+FastPow2(2,Index-3)*(Index-2)%mod)%mod);
         printf("%I64d\n",(FastPow(,Index-)%mod+FastPow(,Index-)*(Index-)%mod)%mod);
     }
     return ;
 }