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;
}