求助，double exp过了，可是这题没过/fad

#include<bits/stdc++.h>
#define F(i,l,r) for(register int i=l;i<=r;i++)
#define ll long long
#define mem(a,b) memset(a,b,sizeof(a))
#define p_b push_back
#define m_p make_pair
#define il inline
using namespace std;
const int N=500005;
int n,m;
int k,u,v;
int a[N];
ll ans[N],pre[N],suff[N],sum[N];
int fr() {
    char ch=getchar();
    int num=0;
    int k=1;
    while((ch>'9'||ch<'0')&&ch!='-') ch=getchar();
    if(ch=='-') {
        k=-1;
        ch=getchar();
    }
    while(ch<='9'&&ch>='0') {
        num=num*10+ch-'0';
        ch=getchar();
    }
    return num*k;
}
il int ls(int x) {return x<<1;}
il int rs(int x) {return x<<1|1;}
il void push_up(int p) {
    sum[p]=sum[ls(p)]+sum[rs(p)];
    pre[p]=max(pre[ls(p)],sum[ls(p)]+pre[rs(p)]);
    suff[p]=max(suff[rs(p)],sum[rs(p)]+suff[ls(p)]);
    ans[p]=max(max(ans[ls(p)],ans[rs(p)]),pre[rs(p)]+suff[ls(p)]);
}
il void build(int p,int l,int r) {
    if(l==r) {
        ans[p]=pre[p]=suff[p]=sum[p]=a[l];
        return ;
    }
    int mid=(l+r)>>1;
    build(ls(p),l,mid);
    build(rs(p),mid+1,r);
    push_up(p);
}
il void upd(int pos,int p,int l,int r,int k) {
    if(l==r) {
        ans[p]=pre[p]=suff[p]=sum[p]=k;
        return ;
    }
    int mid=(l+r)>>1;
    if(pos<=mid) upd(pos,ls(p),l,mid,k);
    else upd(pos,rs(p),mid+1,r,k);
    push_up(p);
}
ll now,lst;
il void query(int ql,int qr,int p,int l,int r) {
    if(ql<=l&&qr>=r) {
        now=max(now,max(ans[p],lst+pre[p]));
        lst=max(suff[p],lst+sum[p]);
        return ;
    }
    int mid=(l+r)>>1;
    if(ql<=mid) query(ql,qr,ls(p),l,mid);
    if(qr>mid) query(ql,qr,rs(p),mid+1,r);
}
int main() {
    n=fr(),m=fr();
    F(i,1,n) a[i]=fr();
    build(1,1,n);
    while(m--) {
        k=fr(),u=fr(),v=fr();
        if(u>v) swap(u,v);
        if(k==1) {
            now=lst=-1e15-7;
            query(u,v,1,1,n);
            printf("%lld\n",now);
        }
        else if(k==2) upd(u,1,1,n,v);
    }
    return 0;
}