## Single Variable

`INF = 0x7fffffff`

The largest value of 32 bit signed int, which is $2^{32} - 1 = 2147483647 \approx{2.147 \times 10^{9}}$

`LLINF = 0x7fffffffffffffff`

（15 fs）

The largest value of 64 bit signed int, which is $2^{64} - 1 = 9223372036854775807 \approx{9.223 \times 10^{18}}$

## memset()

`memset()`

works by bytes. For example, in C++, one int variable takes a room of 4 bytes. So when

```
int var;
memset(var, 0xab, sizeof(var));
```

and `var == 0xabababab`

。

If it is an array, it works by every byte in every element in the array. It is the same as above.

### Common Settings

`memset(a, 0x3f, sizeof(a))`

Similar to `for(int i = 0; i < lim; ++i) a[i] = 0x3f3f3f3f;`

`memset(a, 0x7f, sizeof(a))`

Similar to `for(int i = 0; i < lim; ++i) a[i] = 0x7f7f7f7f;`

`memset(a, 0xff, sizeof(a))`

Similar to `memset(a, -1, sizeof(a))`

or `for(int i = 0; i < lim; ++i) a[i] = -1;`

`memset(a, 0, sizeof(a))`

Obiviously.