Implement ht find

Solves #61 

Note: I assume `s` from the paper being the size (number of buckets) of the hashtable.
Nah, I don't care about it if there are less then 10 lines in the if branch.

```c
if (foo) {
    bar();
    baz();
}
```

or

```c
if (!foo) {
    return;
}
bar();
baz();
```

doesn't make that much difference.