洛谷 三月月赛 B

搞出每一位与前一位的差，然后区间修改只是会影响区间的端点，所以只修改一下端点的值就好。

%%%高一神犇线段树

 #include<bits/stdc++.h>
 #define N 100005
 #define LL long long
 using namespace std;
 inline LL ra()
 {
     int x=,f=; char ch=getchar();
     while (ch<'' || ch>'') {if (ch=='-') f=-; ch=getchar();}
     while (ch>='' && ch<='') {x=x*+ch-''; ch=getchar();}
     return x*f;
 }
 LL S,T,ans,a[N<<],b[N<<];
 int n,Q;
 int main()
 {
     n=ra(); Q=ra(); S=ra(); T=ra();
     for (int i=; i<=n; i++) a[i]=ra();
     for (int i=; i<=n; i++)
     {
         b[i]=a[i]-a[i-];
         if (b[i]>) ans-=S*abs(b[i]);
         if (b[i]<) ans+=T*abs(b[i]);
     }
     while (Q--)
     {
         int l=ra(),r=ra(); LL v=ra();
         if (l>r) swap(l,r);
         if (b[l]>) ans+=S*abs(b[l]);
         if (b[l]<) ans-=T*abs(b[l]);
         b[l]+=v;
         if (b[l]>) ans-=S*abs(b[l]);
         if (b[l]<) ans+=T*abs(b[l]);
         if (r==n) {printf("%lld\n",ans); continue;}
         if (b[r+]>) ans+=S*abs(b[r+]);
         if (b[r+]<) ans-=T*abs(b[r+]);
         b[r+]-=v;
         if (b[r+]>) ans-=S*abs(b[r+]);
         if (b[r+]<) ans+=T*abs(b[r+]);
         printf("%lld\n",ans);
     }
 }