@[huanglinyi](/user/319962) 要求组合数，但是用杨辉三角求会 TLE
by OldDriverTree @ 2023-07-19 21:01:22
20分，杨辉三角代码qwq
```cpp
#include <iostream>
#include <cstdio>
#include <algorithm>
#define int long long
using namespace std;
const int mod = 1000000007;
int n , m;
int jiecheng(int n)
{
int res = 1;
for(int i = 1;i <= n;i++)
{
res *= i;
res %= mod;
}
return res;
}
int C(int m , int n)
{
return jiecheng(n) / jiecheng(n - m) / jiecheng(m);
}
signed main()
{
scanf("%lld %lld" , &n , &m);
printf("%lld" , C(n , m + n));
}
```
by huanglinyi @ 2023-07-19 21:01:33
@[OldDriverTree](/user/681036) 没T，剩下的WA
by huanglinyi @ 2023-07-19 21:01:58
@[huanglinyi](/user/319962) 你这不是杨辉三角求法呀，杨辉三角求法是 $C_i^j=C_{i-1}^j+C_{i-1}^{j-1}$
by OldDriverTree @ 2023-07-19 21:03:46
@[OldDriverTree](/user/681036) 通项公式……
by huanglinyi @ 2023-07-19 21:04:50
@[huanglinyi](/user/319962) 所以这个不是杨辉三角呀
by OldDriverTree @ 2023-07-19 21:05:33
@[huanglinyi](/user/319962) 直接除不逆元，猛
by ACaCaca_ @ 2023-07-19 21:07:44
请学习 模运算 & 逆元
by XeCtera @ 2023-07-19 21:08:15
@[ACaCaca_](/user/320423) 逆元？？？本蒟蒻不知道
by huanglinyi @ 2023-07-19 21:09:52
@[huanglinyi](/user/319962) 不知道逆元你还写组合数的题....
by WYZ20030051 @ 2023-07-19 21:25:59