hdu 4602 Partition

简单题

//#pragma comment(linker, "/STACK:102400000,102400000")#include<iostream>#include<vector>#include<algorithm>#include<cstdio>#include<queue>#include<stack>#include<string>#include<map>#include<set>#include<cmath>#include<cassert>#include<cstring>#include<iomanip>#include<ctime>using namespace std;#ifdef _WIN32typedef __int64 i64;#define out64 "%I64d\n"#define in64 "%I64d"#elsetypedef long long i64;#define out64 "%lld\n"#define in64 "%lld"#endif/************ for topcoder by zz1215 *******************/#define foreach(c,itr)  for(__typeof((c).begin()) itr=(c).begin();itr!=(c).end();itr++)#define FOR(i,a,b)      for( int i = (a) ; i <= (b) ; i ++)#define FF(i,a)         for( int i = 0 ; i < (a) ; i ++)#define FFD(i,a,b)      for( int i = (a) ; i >= (b) ; i --)#define S64(a)          scanf(in64,&a)#define SS(a)           scanf("%d",&a)#define LL(a)           ((a)<<1)#define RR(a)           (((a)<<1)+1)#define pb              push_back#define pf              push_front#define X               first#define Y               second#define CL(Q)           while(!Q.empty())Q.pop()#define MM(name,what)   memset(name,what,sizeof(name))#define MC(a,b)memcpy(a,b,sizeof(b))#define MAX(a,b)        ((a)>(b)?(a):(b))#define MIN(a,b)        ((a)<(b)?(a):(b))#define read            freopen("in.txt","r",stdin)#define write           freopen("out.txt","w",stdout)const int inf = 0x3f3f3f3f;const long long inf64 = 0x3f3f3f3f3f3f3f3fLL;const double oo = 10e9;const double eps = 10e-9;const double pi = acos(-1.0);const int mod = 1000000007;int n, k;int pow2mod(int x){if (x < 0) return 0;int ans = 1;int temp = 2;while (x){if (x & 1){ans = ( (i64)ans*temp ) % mod; }temp = ( (i64)temp*temp) % mod;x >>= 1;}return ans;}int gao(int n,int k){if (k > n) return 0;if (k == n) return 1;return  (pow2mod(n - k) + (((i64)(n - k - 1))*pow2mod(n - k - 2))%mod) % mod;}int main(){int T;cin >> T;while (T--){cin >> n >> k;cout << gao(n, k) << endl;}return 0;}