HUD-4602 Partition 排列

　　题目链接：http://acm.hdu.edu.cn/showproblem.php?pid=4602

　　把n等效为排成一列的n个点，然后就是取出其中连续的k个点。分两种情况，一种是不包含两端，2^( n−k−2 ) ∗ (n−k−1) ，另一种是包含两端：2 ∗ 2^( n – k − 1)。然后特殊情况特判一下。。

 //STATUS:C++_AC_31MS_248KB
 #include <functional>
 #include <algorithm>
 #include <iostream>
 //#include <ext/rope>
 #include <fstream>
 #include <sstream>
 #include <iomanip>
 #include <numeric>
 #include <cstring>
 #include <cassert>
 #include <cstdio>
 #include <string>
 #include <vector>
 #include <bitset>
 #include <queue>
 #include <stack>
 #include <cmath>
 #include <ctime>
 #include <list>
 #include <set>
 #include <map>
 using namespace std;
 //using namespace __gnu_cxx;
 //define
 #define pii pair<int,int>
 #define mem(a,b) memset(a,b,sizeof(a))
 #define lson l,mid,rt<<1
 #define rson mid+1,r,rt<<1|1
 #define PI acos(-1.0)
 //typedef
 typedef __int64 LL;
 typedef unsigned __int64 ULL;
 //const
 const int N=;
 const LL INF=0x3f3f3f3f;
 const int MOD=,STA=;
 const LL LNF=1LL<<;
 const double EPS=1e-;
 const double OO=1e15;
 const int dx[]={-,,,};
 const int dy[]={,,,-};
 const int day[]={,,,,,,,,,,,,};
 //Daily Use ...
 inline int sign(double x){return (x>EPS)-(x<-EPS);}
 template<class T> T gcd(T a,T b){return b?gcd(b,a%b):a;}
 template<class T> T lcm(T a,T b){return a/gcd(a,b)*b;}
 template<class T> inline T lcm(T a,T b,T d){return a/d*b;}
 template<class T> inline T Min(T a,T b){return a<b?a:b;}
 template<class T> inline T Max(T a,T b){return a>b?a:b;}
 template<class T> inline T Min(T a,T b,T c){return min(min(a, b),c);}
 template<class T> inline T Max(T a,T b,T c){return max(max(a, b),c);}
 template<class T> inline T Min(T a,T b,T c,T d){return min(min(a, b),min(c,d));}
 template<class T> inline T Max(T a,T b,T c,T d){return max(max(a, b),max(c,d));}
 //End
 
 int T,n,m;
 
 LL Pow(LL n,int m)
 {
     LL ret=;
     for(;m;m>>=){
         if(m&)ret=(ret*n)%MOD;
         n=(n*n)%MOD;
     }
     return ret;
 }
 
 int main()
 {
  //   freopen("in.txt","r",stdin);
     int i,j;
     scanf("%d",&T);
     while(T--)
     {
         scanf("%d%d",&n,&m);
         if(m>n)
             printf("0\n");
         else if(n==m)
             printf("1\n");
         else
             printf("%I64d\n",(Pow(,n-m)+(m<n-?(n-m-)*Pow(,n-m-):))%MOD);
     }
     return ;
 }