[BZOJ2982]combination Lucas定理

题目链接：http://www.lydsy.com/JudgeOnline/problem.php?id=2982

$C(N,M)\% P = C(N\% P,M\% P) * C(N/P,M/P)\% P$

 #include<cstdio>
 #include<cstring>
 #include<algorithm>
 using namespace std;
 const int mod=1e4+;
 int inv[],fac[];
 int C(int x,int y){
     if(x<y) return ;
     return fac[x]*inv[fac[y]]%mod*inv[fac[x-y]]%mod;
 }
 int main(){
     inv[]=;for(int i=;i<;i++) inv[i]=(mod-mod/i)*inv[mod%i]%mod;
     fac[]=;for(int i=;i<;i++) fac[i]=fac[i-]*i%mod;
     int Test;
     scanf("%d",&Test);
     while(Test--){
         int N,M;
         scanf("%d%d",&N,&M);
         if(N<M){
             puts("");
             continue;
         }
         int Ans=;
         while(M){
             Ans=Ans*C(N%mod,M%mod)%mod;
             N/=mod;
             M/=mod;
         }
         printf("%d\n",Ans);
     }
     return ;
 }