拉格朗日插值法学习

有几个很好的博客：

https://www.cnblogs.com/ECJTUACM-873284962/p/6833391.html

 

洛谷模板：

// luogu-judger-enable-o2
#include<algorithm>
#include<iostream>
#include<cstdlib>
#include<cstring>
#include<cstdio>
#include<cmath>
#include<queue>
#define ll long long
#define dul(p) (((p)%MOD+MOD)%MOD)
using namespace std;
const int maxn=1000000+10101;
const int MOD=998244353;
inline ll read(){
    ll x=0,f=1;char ch=getchar();
    for(;!isdigit(ch);ch=getchar())if(ch=='-')f=-1;
    for(;isdigit(ch);ch=getchar())x=(x<<3)+(x<<1)+ch-'0';
    return x*f;
}
ll ans,n,k,x[maxn],y[maxn];
ll power(ll x,ll y){
    ll ans=1;
    while(y){
        if(y&1)ans=(ans*x)%MOD;
        x=(x*x)%MOD;
        y>>=1;
    }
    return dul(ans);
}
int main(){
    n=read();k=read();
    for(int i=1;i<=n;i++)x[i]=read(),y[i]=read();
    for(int i=1;i<=n;i++){
        ll a1=1,b1=1;
        for(int j=1;j<=n;j++){
            if(i==j)continue;
            a1=a1*(k-x[j])%MOD;
            b1=b1*(x[i]-x[j])%MOD;
        }
        ans=dul(ans+dul(y[i]*a1%MOD*power(b1,MOD-2)));
    }
    printf("%lld",dul(ans));
    return 0;
}

 

转载于:https://www.cnblogs.com/wzq--boke/p/10061529.html