写出式子后前缀和乱搞
#include<iostream> #include<cstdio> #include<cstring> #include<vector> #include<algorithm> using namespace std; typedef long long ll; const int N=3e5+10; const int mod=1000000007; ll a[N],b[N]; ll s[N]; ll pos[N]; ll c[N]; int cal1(int x,int l,int r){ ll res=0; ll tmp=s[r]-s[l-1]; tmp=tmp%mod*pos[x]%mod; return (c[r]-c[l-1]-tmp+mod+mod)%mod; } int cal2(int x,int l,int r){ ll res=0; ll tmp=s[r]-s[l-1]; tmp=tmp%mod*pos[x]%mod; return (tmp-(c[r]-c[l-1])+2*mod)%mod; } int main(){ int n,m; cin>>n>>m; int i; for(i=2;i<=n;i++){ scanf("%lld",&a[i]); pos[i]=(pos[i-1]+a[i])%mod; } for(i=1;i<=n;i++){ scanf("%lld",&b[i]); s[i]=(s[i-1]+b[i])%mod; c[i]=(c[i-1]+b[i]*pos[i])%mod; } while(m--){ int l,r,x; scanf("%d%d%d",&x,&l,&r); if(x<=l){ int ans=0; ans=cal1(x,l,r); printf("%d\n",ans%mod); } else if(x>=r){ int ans=0; ans=cal2(x,l,r); printf("%d\n",ans%mod); } else{ int ans=0; ans=cal1(x,x,r)+cal2(x,l,x); printf("%d\n",ans%mod); } } }