Segment Tree with Lazy Propagation - Range Sum

long long a[100000+50];

long long seg[400000+50];

long long lazy[400000+50];

void build(int node,int l,int r){
    if(l==r){
        
        // cout<<node<<" : "<<a[l]<<"\n";
        seg[node]=a[l];
        return;
    }
    
    int mid=(l+r)/2;
    build(2*node+1,l,mid);
    build(2*node+2,mid+1,r);
    // cout<<node<<" ::: "<<__gcd(seg[2*node+1],seg[2*node+2])<<"\n";
    seg[node]=seg[2*node+1]+seg[2*node+2];
}

long long query(int node,int l,int r,int ql,int qr){
    
    if(lazy[node]){
        seg[node]+=lazy[node]*(r-l+1LL);
        // cout<<node<<" : "<<lazy[node]<<" : ( "<<l<<" , "<<r<<" )\n";
        if(l!=r){
            lazy[2*node+1]+=lazy[node];
            lazy[2*node+2]+=lazy[node];
        }
        lazy[node]=0;
    }
    // cout<<"l = "<<l<<" , r = "<<r<<" , ql= "<<ql<<" , qr = "<<qr<<"\n";
    if(l==r){
        if(ql<=l&&qr>=r){
            // cout<<"1st return value = "<<seg[node]<<"\n";
            // cout<<"When "<<"l = "<<l<<" , r = "<<r<<" , ql= "<<ql<<" , qr = "<<qr<<"\n";
            return seg[node];
        }
        else{
            return 0;
        }
    }
    
    //full overlap
    if(ql<=l&&qr>=r){
        // cout<<"2nd return value = "<<seg[node]<<"\n";
        // cout<<"When "<<"l = "<<l<<" , r = "<<r<<" , ql= "<<ql<<" , qr = "<<qr<<"\n";
        return  seg[node];
    }
    else if(qr<l||ql>r){
        // cout<<"ni/gga\n";
        return 0;
    }
    
    int mid=(l+r)/2;
    int le=query(2*node+1,l,mid,ql,qr);
    int ri=query(2*node+2,mid+1,r,ql,qr);
    if(le==-1&&ri==-1){
        return 0;
    }
    return le+ri;
}


void update(int node,int l,int r,int ql,int qr,long long val){
    
    if(lazy[node]){
        seg[node]+=lazy[node]*(r-l+1LL);
        if(l!=r){
            lazy[2*node+1]+=lazy[node];
            lazy[2*node+2]+=lazy[node];
        }
        lazy[node]=0;
    }    
    
    if(l>r||l>qr||r<ql){
        return;//if no overlap
    }
    
    //full overlap
    if(ql<=l&&qr>=r){
        seg[node]+=val*(r-l+1LL);
        if(l!=r){
            lazy[2*node+1]+=val;
            lazy[2*node+2]+=val;    
        }
        
    }
    else{
        int mid=(l+r)/2;
        update(2*node+1,l,mid,ql,qr,val);
        update(2*node+2,mid+1,r,ql,qr,val);
        seg[node]=seg[2*node+1]+seg[2*node+2];
    }
    // cout<<node<<" ,,,, "<<__gcd(seg[2*node+1],seg[2*node+2])<<"\n";
    
}