借帖说一声，如果你 WA #2 #7 #9，请看一下数据范围，有加法。
by wuwendongxi @ 2021-08-18 20:22:09
@[wuwendongxi](/user/299811) 啥意思？
by Li_Yi_Xuan @ 2022-04-24 13:49:01
[我也是](https://www.luogu.com.cn/record/74513223)
```cpp
# include <bits/stdc++.h>
using namespace std;
typedef long long LL;
const LL N=2001,mod=1e5+3;
LL a,b,c,d,k;
LL fac[N],inv_fac[N];
LL qmi(LL a,LL b)
{
a%=mod;
LL ans=1;
for( ;b;b>>=1)
{
if(b&1) ans=(ans*a)%mod;
a=(a*a)%mod;
}
return ans;
}
void init()
{
fac[0]=inv_fac[0]=1;
for(int i=1;i<N;i++)
{
fac[i]=(i*fac[i-1])%mod;
inv_fac[i]=qmi(fac[i],mod-2);
}
return;
}
LL A(LL n,LL m)
{
return (fac[n]*inv_fac[n-m])%mod;
}
LL C(LL n,LL m)
{
return (((fac[n]*inv_fac[n-m])%mod)*inv_fac[m])%mod;
}
int main()
{
init();
cin>>a>>b>>c>>d>>k;
c+=a;
LL ans=0;
for(LL i=0;i<=k&&i<=a&&i<=b;i++) ans=(ans+((((A(a,i)*C(b,i))%mod)%mod)*(((A(c-i,k-i)*C(d,k-i))%mod)%mod))%mod)%mod;
cout<<ans;
return 0;
}
```
by Li_Yi_Xuan @ 2022-04-24 13:50:57
[AC记录](https://www.luogu.com.cn/record/74601252)
```cpp
# include <bits/stdc++.h>
using namespace std;
typedef long long LL;
const LL N=2001,mod=1e5+3;
LL a,b,c,d,k;
LL fac[N],inv_fac[N];
LL qmi(LL a,LL b)
{
a%=mod;
LL ans=1;
for( ;b;b>>=1)
{
if(b&1) ans=(ans*a)%mod;
a=(a*a)%mod;
}
return ans;
}
void init()
{
fac[0]=inv_fac[0]=1;
for(int i=1;i<N;i++)
{
fac[i]=(i*fac[i-1])%mod;
inv_fac[i]=qmi(fac[i],mod-2);
}
return;
}
LL A(LL n,LL m)
{
if(m>n) return 0;//加一个特判
return (fac[n]*inv_fac[n-m])%mod;
}
LL C(LL n,LL m)
{
if(m>n) return 0;//加一个特判
return (((fac[n]*inv_fac[n-m])%mod)*inv_fac[m])%mod;
}
int main()
{
init();
cin>>a>>b>>c>>d>>k;
c+=a;
LL ans=0;
//这里循环不能多加条件
for(LL i=0;i<=k;i++) ans=(ans+((((A(a,i)*C(b,i))%mod)%mod)*(((A(c-i,k-i)*C(d,k-i))%mod)%mod))%mod)%mod;
cout<<ans;
return 0;
}
```
by Li_Yi_Xuan @ 2022-04-26 13:45:23