蒟蒻54pts求助 WA #7-11

#include<bits/stdc++.h>
#define int long long
using namespace std;
const int maxn = 1e6 + 1;
const int maxm = maxn << 2;
int n,q,opt,x,y,a[maxn];
struct SegmentTree{
    int Max;
    int Maxl,Maxr;
    int Sum;
}tr[maxm];
int lson(int now){return now << 1;}
int rson(int now){return now << 1 | 1;} 
void pushup(SegmentTree &now,const SegmentTree &Lson,const SegmentTree &Rson){
    if(Lson.Maxr < 0 && Rson.Maxl < 0) now.Max = max(Lson.Maxr,Rson.Maxl);
    else{
        now.Max = 0;
        if(Lson.Maxr > 0) now.Max += Lson.Maxr;
        if(Rson.Maxl > 0) now.Max += Rson.Maxl;
    }
    now.Max = max(now.Max,max(Lson.Max,Rson.Max));
    now.Maxl = max(Lson.Maxl,Rson.Maxl + Lson.Sum);
    now.Maxr = max(Rson.Maxr,Lson.Maxr + Rson.Sum);
    now.Sum = Lson.Sum + Rson.Sum;
}
void build(int now,int l,int r){
    if(l == r){
        scanf("%lld",&a[now]);
        tr[now].Max = tr[now].Maxl = tr[now].Maxr = tr[now].Sum = a[now];
        return;
    }
    int mid = (l + r) >> 1;
    build(lson(now),l,mid);
    build(rson(now),mid+1,r);
    pushup(tr[now],tr[lson(now)],tr[rson(now)]);
}
void update(int now,int l,int r,int x,int k){
    if(l == r){
        tr[now].Max = tr[now].Maxl = tr[now].Maxr = tr[now].Sum = k;
        return;
    }
    int mid = (l + r) >> 1;
    if(x <= mid) update(lson(now),l,mid,x,k);
    else update(rson(now),mid+1,r,x,k);
    pushup(tr[now],tr[lson(now)],tr[rson(now)]);
}
SegmentTree query(int now,int l,int r,int L,int R){
    if(L <= l && r <= R) return tr[now];
    int mid = (l + r) >> 1;
    if(L <= mid && R > mid){
        SegmentTree tmp;
        pushup(tmp,query(lson(now),l,mid,L,R),query(rson(now),mid+1,r,L,R));
        return tmp;
    }
    else if(L <= mid) return query(lson(now),l,mid,L,R);
    else return query(rson(now),mid+1,r,L,R);
}
signed main(){
    scanf("%lld%lld",&n,&q);
    //for(int i=1;i<=n;i++) scanf("%d",&a[i]);
    build(1,1,n);
    while(q--){
        scanf("%lld%lld%lld",&opt,&x,&y);
        if(opt == 1){
            if(x > y) swap(x,y);
            printf("%lld\n",query(1,1,n,x,y).Max);
        }
        else update(1,1,n,x,y);
    }
    return 0;
}