hdoj 3037 lucas定理+逆元

#include<cstdio>
#define LL long long
LL f[100005];
void init(LL n)
{
f[0] = 1;
for(int i=1;i<=n;i++)
{
f[i] = f[i-1]*i;
f[i]%=n;
}
}
int inv(LL i,int mod)
{
if(i==1)return 1;
else return inv((mod%i),mod)%mod*(mod-mod/i)%mod;
}
LL lucas(int n,int m,int mod)
{
LL ans = 1;
while(n&&m)
{
LL a = n%mod,b = m%mod;
if(a<b)return 0;
ans*=f[a]%mod*inv(f[b]*f[a-b]%mod,mod)%mod;
ans%=mod;
n/=mod;
m/=mod;
}
return ans;
}
int main()
{
int n,m,p,t;
scanf("%d",&t);
while(t--)
{
scanf("%d%d%d",&n,&m,&p);
init(p);
printf("%I64d\n",lucas(n+m,m,p));
}
return 0;
}