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题目

#include <bits/stdc++.h>
using namespace std;
#define int long long
const int N=1e6+10;
int n, m;
int sum[N << 2], a[N];
int lazy[N << 2];
int p;
int l, r, x;
int b[N << 2];
int cover[N << 2];
void push_up(int pos) {
	sum[pos] = max (sum[pos << 1], sum[pos << 1|1]);
}
void push_down(int pos, int l, int r) {
	if(b[pos]) {
		sum[pos << 1] = sum[pos << 1|1] = cover[pos];
		cover[pos << 1] = cover[pos << 1|1] = cover[pos];
		lazy[pos << 1] = lazy[pos << 1|1] = 0;
		lazy[pos] = cover[pos] = b[pos] = 0;
		b[pos << 1] = b[pos << 1|1] = 1;
	}
	if(lazy[pos]) {
		lazy[pos << 1] += lazy[pos];
		lazy[pos << 1|1] += lazy[pos];
		sum[pos << 1] += lazy[pos];
		sum[pos << 1|1] += lazy[pos];
		lazy[pos] = 0;
	}
}
void build(int pos, int l, int r) {
	if (l == r) {
		sum[pos] = a[l];
		return;
	}
	int mid = l+r >> 1;
	build(pos << 1, l, mid);
	build(pos << 1|1, mid+1, r);
	push_up(pos);
}
void add(int pos, int l, int r, int x, int y, int num) {
	if (x <= l && y >= r) {
		lazy[pos] += num;
		sum[pos] += num;
		return;
	}
	push_down(pos, l, r);
	int mid = l+r >> 1;
	if (x <= mid) {
		add(pos << 1, l, mid, x, y, num);
	}
	if (y > mid) {
		add(pos << 1|1, mid+1, r, x, y, num);
	}
	push_up(pos);
}
int find(int pos, int l, int r, int x, int y) {
	if (x <= l && y >= r) {
		return sum[pos];
	}
	push_down(pos, l, r);
	int mid = l+r >> 1;
	int ans=LLONG_MIN;
	if (x <= mid) {
		ans = max (ans, find(pos << 1, l, mid, x, y));
	}
	if (y>mid) {
		ans = max (ans, find(pos << 1|1, mid+1, r, x, y));
	}
	return ans;
}
void update(int pos, int l, int r, int x, int y, int num) {
	if (x <= l && y >= r) {
		sum[pos] = num;
		lazy[pos] = 0;
		cover[pos] = num;
		b[pos] = 1;
		return;
	}
	push_down(pos, l, r);
	int mid = l+r >> 1;
	if (x <= mid) {
		update (pos << 1, l, mid, x, y, num);
	}
	if (y>mid) {
		update (pos << 1|1, mid+1, r, x, y, num);
	}
	push_up(pos);
}
signed main() {
	cin >> n >> m;
	for (int i=1; i<=n; i++) {
		cin >> a[i];
	}
	build(1, 1, n);
	while (m--) {
		cin >> p;
		if (p == 1) {
			cin >> l >> r >> x;
			update (1, 1, n, l, r, x);
		}
		if (p == 2) {
			cin >> l >> r >> x;
			add (1, 1, n, l, r, x);
		}
		if (p == 3) {
			cin >> l >> r;
			cout << find (1, 1, n, l, r) << '\n';
		}
	}
	return 0;
}