HDU 3073 Saving Beans

 1 #include <bits/stdc++.h>
 2 using namespace std;
 3 typedef long long LL;
 4 LL F[100010] = {1};
 5 void init(LL mod) {
 6     for(int i = 1; i <= mod; ++i)
 7         F[i] = F[i-1]*i%mod;
 8 }
 9 LL gcd(LL a,LL b,LL &x,LL &y) {
10     if(!b) {
11         x = 1;
12         y = 0;
13         return a;
14     }
15     LL ret = gcd(b,a%b,y,x);
16     y -= x*(a/b);
17     return ret;
18 }
19 LL Inv(LL b,LL mod) {
20     LL x,y,d = gcd(b,mod,x,y);
21     return d == 1?(x%mod + mod)%mod:-1;
22 }
23 LL inv(LL b,LL mod) {
24     if(b == 1) return 1;
25     return inv(mod%b,mod)*(mod-mod/b)%mod;
26 }
27 LL Lucas(LL n,LL m,LL mod) {
28     LL ret = 1;
29     while(n && m) {
30         LL a = n%mod;
31         LL b = m%mod;
32         if(a < b) return 0;
33         ret = ret*F[a]%mod*Inv(F[b]*F[a-b]%mod,mod)%mod;
34         n /= mod;
35         m /= mod;
36     }
37     return ret;
38 }
39 int main() {
40     int kase,n,m,mod;
41     scanf("%d",&kase);
42     while(kase--) {
43         scanf("%d%d%d",&n,&m,&mod);
44         init(mod);
45         printf("%I64d\n",Lucas(n+m,n,mod));
46     }
47     return 0;
48 }