线段树求助

初学线段树，样例都过不了……

#include <bits/stdc++.h>
#define int long long
using namespace std;
const int N = 1e5 + 5;
int n, m, a[N], tree[N << 2], tag[N << 2], ch[N << 2], op, l, r, d;
int ls (int x){return x << 1;}
int rs (int x){return x << 1 | 1;}
void change_tag (int x, int l, int r, int d)
{
    ch[x] = d;
    tree[x] = (r - l + 1) * d;
}
void add_tag (int x, int l, int r, int d)
{
    if (ch[x])
    {
        change_tag (x, l, r, ch[x]);
        tag[x] = 0;
    }
    tag[x] += d;
    tree[x] += (r - l + 1) * d;
}
void push_up (int x){tree[x] = max (tree[ls (x)], tree[rs (x)]);}
void push_down (int x, int l, int r)
{
    int mid = (l + r) >> 1;
    if (tag[x])
    {
        add_tag (ls (x), l, mid, tag[x]);
        add_tag (rs (x), mid + 1, r, tag[x]);
        tag[x] = 0;
    }
}
void build (int x, int l, int r)
{
    if (l == r){tree[x] = a[l];return;}
    int mid = (l + r) >> 1;
    build (ls (x), l, mid);
    build (rs (x), mid + 1, r);
    push_up (x);
}
void update1 (int x, int l, int r, int d, int L, int R)
{
    if (L <= l && r <= R)
    {
        add_tag (x, l, r, d);
        return;
    }
    push_down (x, l, r);
    int mid = (l + r) >> 1;
    if (L <= mid)update1 (ls (x), l, mid, d, L, R);
    if (mid < R)update1 (rs (x), mid + 1, r, d, L, R);
    push_up (x);
}
void update2 (int x, int l, int r, int d, int L, int R)
{
    if (L <= l && r <= R)
    {
        change_tag (x, l, r, d);
        return;
    }
    push_down (x, l, r);
    int mid = (l + r) >> 1;
    if (l <= mid)update2 (ls (x), l, mid, d, L, R);
    if (mid < R)update2 (rs (x), mid + 1, r, d, L, R);
}
int query (int x, int l, int r, int L, int R)
{
    if (L <= l && r <= R)return tree[x];
    push_down (x, l, r);
    int mid = (l + r) >> 1, ans = -1e18;
    if (L <= mid)ans = max (query (ls (x), l, mid, L, R), ans);
    if (mid < R)ans = max (query (rs (x), mid + 1, r, L, R), ans);
    return ans;
}
signed main ()
{
    ios::sync_with_stdio (0), cin.tie (0), cout.tie (0);
    cin >> n >> m;
    for (int i = 1; i <= n; ++ i)cin >> a[i];
    build (1, 1, n);
    while (m --)
    {
        cin >> op >> l >> r;
        if (op < 3)
        {
            cin >> d;
            if (op == 1)update2 (1, 1, n, d, l, r);
            else update1 (1, 1, n, d, l, r);
        }
        else cout << query (1, 1, n, l, r) << '\n';
    }
    return 0;
}