Hi,

I'm working on my time complexity understanding in C++. Right now, I'm trying to figure it out, and kinda got some of them, such as:

constant O(1):

```
int first(int N){
int i = N;
int x = 0;
x++;
return x;
}
```

O(n)

```
int second(int N){
int sum = 0,
i = 0;
const int n = N;
while(i < n){
sum += i;
i++;
}
return i;
}
```

and O(n^2)

```
int third(int N){
int count = 0,
count1 = 0,
count2 = 0,
n = N;
for(count1 = 1; count1 <= n; count1++){
for(count2 = 1; count2 <= n; count2++){
int i = 0;
i++;
}
}
count = count1 + count2;
return count;
}
```

These might be wrong, since I'm a little confused about all this.

But, I'm totally not sure about the O(n^3) (do I need 3 loops???), O(log n), and O(n log n) (this one is just throwing me off)...

Any help would be appreciated :)

Thanks