洛谷 3932 浮游大陆的68号岛 前缀和

#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
#include<cstdlib>
using namespace std;
typedef long long ll;

const ll MAXN=300001,Mod=19260817;
ll lsum[MAXN],rsum[MAXN],lnum[MAXN],rnum[MAXN];
ll dis[MAXN],num[MAXN];
ll la[MAXN],ra[MAXN];
ll n,m,ans;

void solve()
{
scanf("%lld%lld",&n,&m);
for(int i=2;i<=n;i++)
{
scanf("%lld",&dis[i]);
rsum[i]=(rsum[i-1]+dis[i])%Mod;
}
for(int i=1;i<=n;i++)
{
scanf("%lld",&num[i]);
rnum[i]=(rnum[i-1]+num[i])%Mod;
ra[i]=(ra[i-1]+(num[i]*rsum[i]))%Mod;
}

for(int i=n;i>=1;i--)
{
lsum[i]=((rsum
-rsum[i])%Mod+Mod)%Mod,lnum[i]=((rnum
-rnum[i-1])%Mod+Mod)%Mod;
la[i]=(la[i+1]+(num[i]*lsum[i]))%Mod;
}
ll x,l,r;
while(m--)
{
scanf("%lld%lld%lld",&x,&l,&r);
ans=0;
if(x<=l)//从右往左走;
ans=(ra[r]-ra[l-1]-(rsum[x]*(rnum[r]-rnum[l-1]))%Mod)%Mod;
else if(x>=r)//从左往右走;
ans=(la[l]-la[r+1]-(lsum[x]*(lnum[l]-lnum[r+1]))%Mod)%Mod;
else if(x<r && x>l)
ans=(ra[r]-ra[x-1]-(rsum[x]*(rnum[r]-rnum[x-1]))%Mod+la[l]-la[x+1]-(lsum[x]*(lnum[l]-lnum[x+1]))%Mod)%Mod;
while(ans<0) ans+=Mod;
printf("%lld\n",ans);
}
}

int main()
{
solve();
return 0;
}