大组合数取余模板【Lucas定理】
求C(n, m) % mod
|
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
|
#include <bits/stdc++.h>using namespace std;
long long fact[200200];
long long inv[200200];
const int mod = 1e9 + 7;
long long qpow(long long x, long long n)
{ long long ans = 1;
while (n)
{
if (n & 1)
ans = ans * x % mod;
x = x * x % mod;
n >>= 1;
}
return ans;
}void init()
{ fact[0] = 1;
for (int i = 1; i < 200005; i++)
fact[i] = fact[i - 1] * i % mod;
for (int i = 0; i < 200005; i++)
inv[i] = qpow(fact[i], mod - 2);
}long long C(int n, int m)
{ return fact[n] * inv[n - m] % mod * inv[m] % mod;
}int main()
{ init();
int n, m;
while(cin >> n >> m) {
cout << C(n, m) << endl;
}
} |