求助线段树（悬赏关注）

#include<bits/stdc++.h>

using namespace std;

const int MAXN = 1000010;

int a[MAXN]; //输入数组

int Ans;

struct
{
    int l, r; //表示某个节点代表的区间
    int sum; //区间和，也可以区间最大最小值
    int lz; //懒惰标记
}tree[MAXN];

void build(int i, int l, int r) //通用
{
    tree[i].l = l, tree[i].r = r;
    if(l == r)
    {
        tree[i].sum = a[l];
        return;
    }
    int mid = (l + r) >> 1;
    build(i * 2, l, mid);
    build(i * 2 + 1, mid + 1, r);
    tree[i].sum = tree[i * 2].sum + tree[i * 2 + 1].sum;
}

void push_down(int i) //把懒惰标记向下移
{
    if(tree[i].lz != 0)
    {
        tree[i * 2].lz += tree[i].lz;
        tree[i * 2 + 1].lz += tree[i].lz;
        int mid = (tree[i].l + tree[i].r) / 2;
        tree[i * 2].sum += tree[i].lz * (mid - tree[i].l + 1);
        tree[i * 2 + 1].sum += tree[i].lz * (tree[i].r - mid); //千万不要再加1了
        tree[i].lz = 0;
        //不用将sum清空
    }
    return;
}

void add(int i, int l, int r, int k) //区间修改
{
    if(tree[i].l >= l && tree[i].r <= r)
    {
        tree[i].sum += k * (tree[i].r - tree[i].l + 1);
        tree[i].lz += k; //向下传递懒惰标记
        return;
    }
    push_down(i);
    if(tree[i * 2].r >= l) add(i * 2, l, r, k);
    if(tree[i * 2 + 1].l <= r) add(i * 2 + 1, l, r, k);
    tree[i].sum = tree[i * 2].sum + tree[i * 2 + 1].sum; //有关区间的add要加上这个
}

int get_sum(int i, int l, int r) //区间查询
{
    if(tree[i].l >= l && tree[i].r <= r)
        return tree[i].sum;
    if(tree[i].r < l || tree[i].l > r)
        return 0;
    push_down(i);

    int res = 0;
    if(tree[i * 2].r >= l) res += get_sum(i * 2, l, r);
    if(tree[i * 2 + 1].l <= r) res += get_sum(i * 2 + 1, l, r);
    return res;
}

int main()
{
    int n, t, op, x, y, z;
    cin >> n >> t;
    for(int i = 1; i <= n; i++)
    {
        cin >> a[i];
    }
    build(1,1,n);
    while(t--)
    {
        cin >> op;
        if(op == 1)
        {
            cin >> x >> y >> z;
            add(1, x, y, z);
        }
        else
        {
            cin >> x >> y;
            cout << get_sum(1, x, y) << endl;
        }
    }
    return 0;
}

8 9 10三个点WA了