第二次写线段树， 刚从线段树1过来的， 不太熟悉， 帮看一下，谢谢!

#include <iostream>
#include <cstdio>
using namespace std;

#define LL long long

const LL N = 1e6 + 10;
const LL INF = 9223372036854775807;

LL read() {
	LL x = 0;
	LL f = 1;
	char c = getchar();
	while(c > '9' || c < '0') {
		if(c == '-') f = -1;
		c = getchar();
	}
	while(c <= '9' && c >= '0') {
		x = x * 10 + (c - '0');
		c = getchar();
	}
	return x * f;
}

void write(LL x) {
	if(x < 0) x = -x, putchar('-');
	if(x > 9) write(x / 10);
	putchar(x % 10 + '0');
}

int n, q;

LL a[N];

LL MAX[N * 4];
LL mark[N * 4];

LL f[N * 4];
LL prom[N * 4]; 

void push_down(LL t) {
	if(f[t]) {
		prom[t * 2] = prom[t];
		prom[t * 2 + 1] = prom[t];
		MAX[t * 2] = prom[t];
		MAX[t * 2 + 1] = prom[t];
		
		mark[t] = 0;
		mark[t * 2] = 0;
		mark[t * 2 + 1] = 0;
		
		prom[t] = 0;
		f[t] = false;
		f[t * 2] = true;
		f[t * 2 + 1] = true;
	}
	else {
		mark[t * 2] += mark[t];
		mark[t * 2 + 1] += mark[t];
		MAX[t * 2] += mark[t];
		MAX[t * 2 + 1] += mark[t];
		mark[t] = 0;
	}
}

void build(LL l, LL r, LL t) {
	if(l == r) MAX[t] = a[l];
	else {
		LL mid = (l + r) >> 1;
		build(l, mid, t * 2);
		build(mid + 1, r, t * 2 + 1);
		MAX[t] = max(MAX[t * 2], MAX[t * 2 + 1]);
	}
}

void update(LL L, LL R, LL l, LL r, LL t, LL val, LL op) {
	if(r < L || l > R) return ;
	else if(l >= L && r <= R) {
		if(op == 1) {
			f[t] = true;
			if(l < r) prom[t] = val;
			MAX[t] = val;
		}
		else {
			MAX[t] += val;
			if(l < r) mark[t] += val;
		}
	}
	else {
		LL mid = (l + r) >> 1;
		push_down(t);
		update(L, R, l, mid, t * 2, val, op);
		update(L, R, mid + 1, r, t * 2 + 1, val, op);
		MAX[t] = max(MAX[t * 2], MAX[t * 2 + 1]);
	}
}

LL query(LL L, LL R, LL l, LL r, LL t) {
	if(r < L || l > R) return -INF;
	else if(l >= L && r <= R) {
		return MAX[t];
	}
	else {
		LL mid = (l + r) >> 1;
		push_down(t);
		LL L_MAX = query(L, R, l, mid, t * 2);
		LL R_MAX = query(L, R, mid + 1, r, t * 2 + 1);
		return max(L_MAX, R_MAX);
	}
}

int main()
{
	n = read();
	q = read();
	for(int i = 1; i <= n; i ++) a[i] = read();
	
	build(1, n, 1);
	
	for(int i = 1; i <= q; i ++) {
		LL op, l, r, x;
		op = read();
		if(op == 1) {
			l = read();
			r = read();
			x = read();
			update(l, r, 1, n, 1, x, 1);
		}
		else if(op == 2) {
			l = read();
			r = read();
			x = read();
			update(l, r, 1, n, 1, x, 2);
		}
		else {
			l = read();
			r = read();
			write(query(l, r, 1, n, 1));
			putchar('\n');
		}
	}
	return 0;
}