1009. Complement of Base 10 Integer
- idea is to take all the bits and XOR them.
- we were unaware of the size, so we did find that out first.
- there are more optimal approach, will add them.
implementation
```cpp
int bitwiseComplement(int n) {
if (n == 0) return 1;
int temp = n;
int Size = 0;
while (temp) {
temp = temp >> 1;
Size ++;
}
for (int i = 0; i < Size; i++)
n ^= (1 << i);
return n;
}
```
more concise
```cpp
int bitwiseComplement(int n) {
if (n == 0) return 1;
for (int temp = n, i = 0; (temp > 0); temp = temp >> 1, i++)
n ^= (1 << i);
return n;
}
```