bzoj1856 [Scoi2010]字符串

 1 #include <bits/stdc++.h>
 2 #define il inline
 3 #define RG register
 4 #define ll long long
 5 #define rhl (20100403)
 6 #define N (2000010)
 7 
 8 using namespace std;
 9 
10 int inv[N],fac[N],ifac[N],n,m;
11 
12 il int C(RG int n,RG int m){
13   return 1LL*fac[n]*ifac[m]%rhl*ifac[n-m]%rhl;
14 }
15 
16 int main(){
17 #ifndef ONLINE_JUDGE
18   freopen("string.in","r",stdin);
19   freopen("string.out","w",stdout);
20 #endif
21   cin>>n>>m,fac[0]=ifac[0]=fac[1]=ifac[1]=inv[1]=1;
22   for (RG int i=2;i<=n+m;++i){
23     inv[i]=1LL*(rhl-rhl/i)*inv[rhl%i]%rhl;
24     fac[i]=1LL*fac[i-1]*i%rhl;
25     ifac[i]=1LL*ifac[i-1]*inv[i]%rhl;
26   }
27   printf("%d\n",(C(n+m,n)-C(n+m,n+1)+rhl)%rhl); return 0;
28 }