记录

# include<iostream>
# include<algorithm>
# include<cmath>
# define int long long
# define endl "\n"
using namespace std;
const int maxn=1e6+1, INF=2147483647;
int n, m, a[maxn];
struct Node{
	int l, r, mmax;
	int add, change;
}tree[maxn*4];
void build_tree(int i, int l, int r) {
	tree[i].l=l; tree[i].r=r; tree[i].mmax=-INF; tree[i].change=INF;
	if(l==r) {
		tree[i].mmax=a[l];
		return ;
	}
	int mid=(l+r)/2;
	build_tree(2*i, l, mid);
	build_tree(2*i+1, mid+1, r);
	tree[i].mmax=max(tree[2*i].mmax, tree[2*i+1].mmax);
} 
void push_down(int i) {
	if(tree[i].change!=INF) {
		tree[i*2].mmax=tree[i*2+1].mmax=tree[i].change+tree[i].add;
		tree[i*2].change=tree[i*2+1].change=tree[i].change;
		tree[i*2].add=tree[i*2+1].add=0;
	} else {
		tree[i*2].mmax+=tree[i].add;
		tree[i*2+1].mmax+=tree[i].add;
		tree[i*2].add+=tree[i].add;
		tree[i*2+1].add+=tree[i].add;
	}
	tree[i].change=INF;
	tree[i].add=0;
}
void add(int i, int l, int r, int d) {
	if(tree[i].l>=l && tree[i].r<=r) {
		tree[i].mmax+=d;
		tree[i].add+=d;
		return ;
	}
	push_down(i);
	int mid=(tree[i].l+tree[i].r)/2;
	if(l<=mid) add(2*i, l, r, d);
	if(r>=mid+1) add(2*i+1, l, r, d);
	tree[i].mmax=max(tree[2*i].mmax, tree[2*i+1].mmax);
}
void change(int i, int l, int r, int d) {
	if(tree[i].l>=l && tree[i].r<=r) {
		tree[i].mmax=d;
		tree[i].add=0;
		tree[i].change=d;
		return ;
	}
	push_down(i);
	int mid=(tree[i].l+tree[i].r)/2;
	if(l<=mid) change(2*i, l, r, d);
	if(r>=mid+1) change(2*i+1, l, r, d);
	tree[i].mmax=max(tree[2*i].mmax, tree[2*i+1].mmax);
}
int query(int i, int l, int r) {
	if(tree[i].l>=l && tree[i].r<=r) return tree[i].mmax;
	push_down(i);
	int mid=(tree[i].l+tree[i].r)/2, mmax=0;
	if(l<=mid) mmax=max(mmax, query(2*i, l, r));
	if(r>=mid+1) mmax=max(mmax, query(2*i+1, l, r));
	return mmax;
} 
signed main() {
	cin >> n >> m;
	for(int i=1; i<=n; i++) cin >> a[i];
	build_tree(1, 1, n);
	while(m--) {
		int op; cin >> op;
		if(op==1) {
			int x, y, k; cin >> x >> y >> k;
			change(1, x, y, k);
		} else if(op==2) {
			int x, y, k; cin >> x >> y >> k;
			add(1, x, y, k); 
		} else {
			int x, y; cin >> x >> y;
			cout << query(1, x, y) << endl;
		}
	}
	return 0;
}

qwq