push_down操作有点小问题，改成这样就行了。
```cpp
#include <iostream>
#include <cstdio>
using namespace std;
#define LL long long
#define int long long
const LL N = 1e6 + 10;
const LL INF = 1e18;
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 * 2 + 1] = 0;
mark[t * 2] = 0;
prom[t] = 0;
f[t] = false;
f[t * 2] = true;
f[t * 2 + 1] = true;
}
if(mark[t]){
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(l < r)push_down(t);
if(op == 1) {
f[t] = true;
if(l < r) prom[t] = val,mark[t] = 0;
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) {
if(l < r)push_down(t);
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);
}
}
signed 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;
}
```
by Rainylower @ 2023-11-16 14:30:18
@[Rainylower](/user/275079) 谢谢了!
by Inferior_dust @ 2023-11-17 15:26:01