谔谔
by iiawaKL @ 2020-06-22 22:15:57
@[bovine__kebi](/user/294736)
```cpp
#include<bits/stdc++.h>
using namespace std;
const int Mod=998244353;
const int maxn=2*1e3+5;
int a[maxn],b[maxn],n,k;
inline int qpower(int x,int p)
{
int ans=1;
x%=Mod;
while(p)
{
if(p&1)ans=1ll*ans*x%Mod;
x=1ll*x*x%Mod;
p>>=1;
}
return ans;
}
inline int qwq(int a,int b)
{
return a<b?a+Mod-b:a-b;
}
inline int lagrange()
{
int sum=0;
for(int i=1;i<=n;i++)
{
int x=1,y=1;
for(int j=1;j<=n;j++)
{
if(i==j)continue;
x=1ll*x*qwq(k,a[j])%Mod; // a[j]
y=1ll*y*qwq(a[i],a[j])%Mod;
}
sum=(1ll*sum+(1ll*b[i]*x%Mod*qpower(y,Mod-2)%Mod)%Mod)%Mod;
}
return sum%Mod;
}
int main()
{
scanf("%d %d",&n,&k);
for(int i=1;i<=n;i++)scanf("%d %d",&a[i],&b[i]);
printf("%d\n",lagrange());
}
```
不同的地方帮您注释标了一下
by hly1204 @ 2020-06-22 23:21:46
@[hly1204](/user/242973) 看到了，谢谢Orz
by bovine__kebi @ 2020-06-23 08:00:59