Array Implementation of Set
We want to efficiently implement the Set ADT with an array as the underlying data structure.
Exercise Complete the following table.
| Operation | How? | Runtime |
|---|---|---|
has | ||
insert | ||
remove | ||
size |
Solution
Except for size, all operations require a helper find method to check if an element exists. We cannot keep the underlying data sorted to perform Binary Search (why?). We will, however, explore this option for implementing an array-based OrderedSet ADT. Let's keep the underlying data unsorted and perform Linear Search in find.
| Operation | How? | Runtime |
|---|---|---|
has | return find(t) != -1; | $O(n)$ |
insert | if (fint(t) == -1) data[numElement++] = t; | $O(n)$ |
remove | Find the element, swap with last, numElements-- | $O(n)$ |
size | return numElements; | $O(1)$ |
find | Linear search | $O(n)$ |
Notice the remove strategy, which allows us to spend constant time after the element is found.