建议学习时间复杂度相关内容。
by lizechen @ 2023-02-28 10:55:24
以及其中
```cpp
for(int i = 1 ; i <= c ; i ++){
f[i] == b;
}
```
应当为
```cpp
for(int i = b ; i <= c ; i ++){
f[i] ^= 1;
}
```
by lizechen @ 2023-02-28 10:57:26
哇
by jijidawang @ 2023-02-28 11:05:54
你得用 bitset 优化才能过
by jijidawang @ 2023-02-28 11:07:09