AC Code

#include<bits/stdc++.h>
#include<bits/extc++.h>
#ifndef ONLINE_JUDGE
// #define OPEN_FILE
// #define OPEN_TIME
#endif
#define AC return 0;
#define lowbit(x) (x&(-x))
#define ll long long
#define ull unsigned long long
#define pii pair<int,int>
using namespace std;
const int maxn=1e6+10,INF=0x3f3f3f3f,mod=1e9+7;
const double eps=1e-8,Pi=acos(-1);
mt19937_64 mt(1145);
int n,m;
int a[maxn];
struct Info{
    ll ans,pre,suf,sum;
    Info(){ans=pre=suf=-INF,sum=0;}
    Info(ll a,ll p,ll s,ll t){ans=a,pre=p,suf=s,sum=t;}
    Info(ll x){ans=x,pre=x,suf=x,sum=x;}
    Info operator+(const Info &x)const{
        return {max({ans,x.ans,suf+x.pre}),max(pre,sum+x.pre),max(x.suf,x.sum+suf),sum+x.sum};
    }
};

struct SegTree{
    struct Node{
        Info sum;
    }t[maxn<<2];
#define ls(p) (p<<1)
#define rs(p) (p<<1|1)
#define sum(p) t[p].sum
#define tag(p) t[p].tag
    void PushUp(int p){
        sum(p)=sum(ls(p))+sum(rs(p));
    }
    void Change(int p,int l,int r,int x,Info k){
        if(l==r) return sum(p)=k,void();
        int mid=l+r>>1;
        if(x<=mid) Change(ls(p),l,mid,x,k);
        else Change(rs(p),mid+1,r,x,k);
        PushUp(p);
    }
    Info Query(int p,int l,int r,int L,int R){
        if(L<=l&&R>=r) return sum(p);
        if(l>R||r<L) return {};
        int mid=l+r>>1;
        return Query(ls(p),l,mid,L,R)+Query(rs(p),mid+1,r,L,R);
    }
    Info Query(int l,int r){
        return Query(1,1,n,l,r);
    }
    void Change(int x,Info k){
        Change(1,1,n,x,k);
    }
    void Build(int p,int l,int r){
        sum(p)={};
        if(l==r) return sum(p)={a[l]},void();
        int mid=l+r>>1;
        Build(ls(p),l,mid);
        Build(rs(p),mid+1,r);
        PushUp(p);
    }
}t;

void solve() {
    int opt,x,k;
    while(m--) {
        cin>>opt>>x>>k;
        if(opt==2) t.Change(x,{k});
        else cout<<t.Query(min(x,k),max(x,k)).ans<<"\n";
    }
}
void init() {
    cin>>n>>m;
    for(int i=1;i<=n;++i) 
        cin>>a[i];
    t.Build(1,1,n);
}
int main() {
#ifdef OPEN_FILE
    freopen("in.txt","r",stdin);
    freopen("out.txt","w",stdout);
#endif
#ifdef OPEN_TIME
    auto StartTime=clock();
#endif
    // ios::sync_with_stdio(false),cin.tie(nullptr),cout.tie(nullptr);
    int T=1;
    // cin>>T;
    // while(cin>>n) {
    while(T--) {
        init();
        solve();
    }
#ifdef OPEN_TIME
    cerr<<"used: "<<(double)(clock()-StartTime)/CLOCKS_PER_SEC*1000<<" ms"<<endl;
#endif
    AC
}