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=0,f=1; char ch=getchar();
    while (ch<'0' || ch>'9') {if (ch=='-') f=-1; ch=getchar();}
    while (ch>='0' && ch<='9') {x=x*10+ch-'0'; ch=getchar();}
    return x*f;
}
LL S,T,ans,a[N<<1],b[N<<1];
int n,Q;
int main()
{
    n=ra(); Q=ra(); S=ra(); T=ra();
    for (int i=0; i<=n; i++) a[i]=ra();
    for (int i=1; i<=n; i++)
    { 
        b[i]=a[i]-a[i-1];
        if (b[i]>0) ans-=S*abs(b[i]);
        if (b[i]<0) ans+=T*abs(b[i]);
    }
    while (Q--)
    {
        int l=ra(),r=ra(); LL v=ra();
        if (l>r) swap(l,r);
        if (b[l]>0) ans+=S*abs(b[l]);
        if (b[l]<0) ans-=T*abs(b[l]);
        b[l]+=v;
        if (b[l]>0) ans-=S*abs(b[l]);
        if (b[l]<0) ans+=T*abs(b[l]);
        if (r==n) {printf("%lld
",ans); continue;}
        if (b[r+1]>0) ans+=S*abs(b[r+1]);
        if (b[r+1]<0) ans-=T*abs(b[r+1]);
        b[r+1]-=v;
        if (b[r+1]>0) ans-=S*abs(b[r+1]);
        if (b[r+1]<0) ans+=T*abs(b[r+1]);
        printf("%lld
",ans);
    }
}