关于规范写法

#include<bits/stdc++.h>
using namespace std;
int n,m;
long long a[100005];
template<typename T>
class seg_tree
{
private:
    struct node
    {
        T data,lazy=0;
    };
    vector<node> tree;
    int n=0;
    const T* data_start;
    void build_tree(int idx,int l,int r)
    {
        if(l==r)
        {
            tree[idx].data=data_start[l];
            return;
        }
        int mid=l+(r-l)/2;
        build_tree(idx*2+1,l,mid);
        build_tree(idx*2+2,mid+1,r);
        tree[idx].data=tree[idx*2+1].data+tree[idx*2+2].data;
        return;
    }
    void push_down(int idx,int l,int mid,int r)
    {
        if(tree[idx].lazy)
        {
            tree[idx*2+1].data+=tree[idx].lazy*T(mid-l+1);
            tree[idx*2+1].lazy+=tree[idx].lazy;
            tree[idx*2+2].data+=tree[idx].lazy*T(r-mid);
            tree[idx*2+2].lazy+=tree[idx].lazy;
            tree[idx].lazy=0;
        }
        return;
    }
    T query_tree(int idx,int l,int r,int L,int R)
    {
        if(l>R||r<L) return T{};
        if(L<=l&&r<=R) return tree[idx].data;
        int mid=l+(r-l)/2;
        push_down(idx,l,mid,r);
        return query_tree(idx*2+1,l,mid,L,R)+query_tree(idx*2+2,mid
+1,r,L,R);
    }
    void update_tree(int idx,int l,int r,int L,int R,T k)
    {
        if(l>R||r<L) return;
        if(L<=l&&r<=R)
        {
            tree[idx].data+=k*T(r-l+1),tree[idx].lazy+=k;
            return;
        }
        int mid=l+(r-l)/2;
        push_down(idx,l,mid,r);
        update_tree(idx*2+1,l,mid,L,R,k);
        update_tree(idx*2+2,mid+1,r,L,R,k);
        tree[idx].data=tree[idx*2+1].data+tree[idx*2+2].data;
        return;
    }
public:
    void build(const T* l,const T* r)
    {
        n=distance(l,r),data_start=l;
        tree.resize(4*n);
        build_tree(0,0,n-1);
    }
    T query(const T* L,const T* R)
    {
        int l=distance(data_start,L),r=distance(data_start,R)-1;
        return query_tree(0,0,n-1,l,r);
    }
    void update(const T* L,const T* R,T k)
    {
        int l=distance(data_start,L),r=distance(data_start,R)-1;
        update_tree(0,0,n-1,l,r,k);
        return;
    }
};
int main()
{
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    cin>>n>>m;
    for(int i=1;i<=n;i++) cin>>a[i];
    seg_tree<long long> seg;
    seg.build(a+1,a+n+1);
    for(int i=1,cz,l,r;i<=m;i++)
    {
        cin>>cz>>l>>r;
        if(cz==1)
        {
            long long k;
            cin>>k;
            seg.update(a+l,a+r+1,k);
        }
        else cout<<seg.query(a+l,a+r+1)<<endl;
    }
    return 0;
}