**To retrieve a value with key K:**

- compute P = H(K).
- if P is EMPTY: there is no value for key K.
- if P is OCCUPIED by a value with key K, return it.
- else, compute another P and repeat steps 2-4.

**Additional stopping criterion:** suppose all positions are
marked deleted, then the stopping conditions of steps 2-3 will never
be true.

If P == H(K), we have come full circle!

**Delete Operation:** identical except that in step 3, position
P should just be marked DELETED.

Step 4 captures 2 possibilities:

- position P is DELETED
- position P is OCCUPIED by a value whose key isn't K