C++ Implementation of Hash table with linear probing
1 Task Description
You are asked to use C++ to implement
• Hash table with linear probing
2 Submission Guideline
You must follow this guideline! Your submission will be marked automatically. Failure to
follow this guideline will result in 0.
Your submission should contain exactly one file: main.cpp.
You do not need to submit a design.
You are asked to implement a very specific hash table. The keys are lower-case English words (e.g., apple,
pear). The length of a key is at most 10. The hash function is “simply using the last character”. That is,
the hash value of apple should be e, and the hash value of pear should be r. Your hash table contains exactly
26 slots (hash value a to hash value z). The total number of English words/keys you need to deal with is at
most 26, so the table is never too small.
A table slot has three different statuses: “never used”, “tombstone”, and “occupied”. Table starts with
26 “never used” slots.
Searching works as follows: given a key, take its last character as the hash value. First try the corresponding table slot, if the objective key is there, then you have found it. If the corresponding slot is never
used, terminate because we are certain that the objective is not in the table. If the slot is occupied but it’s
not the objective, or the slot is a “tombstone”, then we move on to the next slot (may need to wrap around
the table if the current slot is the last one). We keep trying until we either find the key or are certain that
the key does not exist in the table.
Insertion works as follows: First perform searching to ensure that the key does not exist. If it already
exists, then do nothing. If it does not, take the last character of a key as the hash value. If the corresponding
table slot is not occupied (either “never used” or “tombstone”), put the key there (the slot is now occupied).
If the corresponding slot is already occupied, try the next slot. Repeat trying until you find an unoccupied
slot.
Deletion works as follows: given a key, use the searching process to locate its slot. (If the key is not in
the table, then do nothing.) Once you find the key, change the slot status to “tombstone”.
You should start your program by initializing an empty hash table. Your program takes one line as
input. The input line contains n “modification moves” separated by spaces (1 ≤ n ≤ 26). The available
modification moves are
• AWord (Character A followed by a lower-case English word of length at most 10): Aapple means insert
key apple into the hash table. If apple is already in the table, do nothing.
• DWord (Character D followed by a lower-case English word of length at most 10): Dapple means delete
key apple from the hash table. If apple is not in the tree, do nothing.
1
At the end, you need to go through the slots from a to z, and output all the keys separated by space.
You don’t need to worry about invalid inputs.
Sample input 1: Aaaa Accc Abbb
Sample output 1: aaa bbb ccc
Sample input 2: Abba Aaaa Acca
Sample output 2: bba aaa cca
Sample input 3: Abba Aaaa Acca Daaa
Sample output 3: bba cca
3 Marking
Marking will be done automatically. The total mark is 10 (1 for compiling and 9 for 9 test cases).
4 Websubmission
You are asked to submit via the web interface https://cs.adelaide.edu.au/services/websubmission/.
The submission steps should be self-explanatory. Simply choose the correct semester, course, and assignment.
The websubmission system will automatically fetch the latest version of your work from your SVN repository
(you may also choose to submit older versions). Once your work is submitted, the system will launch a
script checking the format of your submission. Click “View Feedback” to view the results. Your mark will
be calculated offline after the deadline. You are welcome to resubmit for as many times as you wish (before
the deadline).
We will compile your code using g++ -o main.out -std=c++11 -O2 -Wall main.cpp. It is your responsibility to ensure that your code compiles on the university system.
1g++ has too many versions, so being able to compile on your laptop does not guarantee that it compiles on the university
system. You are encouraged to debug your code on a lab computer (or use SSH).