Hash map vs hash set in Data Structures Theory - Visual Side-by-Side Comparison

Concept Flow - Hash map vs hash set

Start

↓

Input Data

↓

Use Hash Set

|Yes↓

Use Hash Map

↓

Store data with hashing

↓

Retrieve/Search by key

↓

End

Decide if data has key-value pairs; if yes, use hash map, else use hash set. Both use hashing to store and retrieve data efficiently.

Execution Sample

Data Structures Theory

hash_map = {"apple": 3, "banana": 5}
hash_set = {"apple", "banana"}

# Check if "apple" in hash_map
# Check if "apple" in hash_set

Shows storing key-value pairs in a hash map and unique items in a hash set, then checking membership.

Analysis Table

Step	Data Structure	Operation	Input	Internal Action	Output/Result
1	Hash Map	Insert	Key: "apple", Value: 3	Hash key "apple", store ("apple",3)	Stored
2	Hash Map	Insert	Key: "banana", Value: 5	Hash key "banana", store ("banana",5)	Stored
3	Hash Set	Insert	Value: "apple"	Hash value "apple", store unique	Stored
4	Hash Set	Insert	Value: "banana"	Hash value "banana", store unique	Stored
5	Hash Map	Search	Key: "apple"	Hash key "apple", find value	Found: 3
6	Hash Set	Search	Value: "apple"	Hash value "apple", check presence	Found: True
7	Hash Map	Search	Key: "orange"	Hash key "orange", not found	Not Found
8	Hash Set	Search	Value: "orange"	Hash value "orange", not found	Found: False
9	Hash Map	End			No more operations
10	Hash Set	End			No more operations

💡 All insertions and searches completed; no more operations.

State Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	After Step 4	After Step 5	After Step 6	Final
hash_map	{}	{"apple":3}	{"apple":3, "banana":5}	{"apple":3, "banana":5}	{"apple":3, "banana":5}	{"apple":3, "banana":5}	{"apple":3, "banana":5}	{"apple":3, "banana":5}
hash_set	{}	{}	{}	{"apple"}	{"apple", "banana"}	{"apple", "banana"}	{"apple", "banana"}	{"apple", "banana"}
search_result	N/A	N/A	N/A	N/A	N/A	3	True	N/A

Key Insights - 3 Insights

Why does a hash map store key-value pairs but a hash set only stores values?

Because a hash map associates each key with a value for lookup, while a hash set only tracks unique values without associated data, as shown in steps 1-4 of the execution_table.

Can a hash set tell you the value associated with an element like a hash map?

No, a hash set only tells if a value exists or not (True/False), it does not store or return associated values, as seen in steps 6 and 8.

What happens if you search for a key/value that does not exist?

The search returns 'Not Found' for hash map or False for hash set, indicating absence, as shown in steps 7 and 8.

Visual Quiz - 3 Questions

Look at the execution_table at step 5, what is the output when searching for key "apple" in the hash map?

A Found: True

B Found: 3

C Not Found

D Found: False

💡 Hint

Refer to the 'Output/Result' column at step 5 in the execution_table.

At which step does the hash set first store the value "banana"?

A Step 2

B Step 3

C Step 4

D Step 5

💡 Hint

Check the 'Operation' and 'Input' columns for hash set insertions in the execution_table.

If you tried to store a key-value pair in a hash set, what would happen according to the concept flow?

A It cannot store key-value pairs, so use a hash map instead

B It ignores the value and stores only the key

C It stores the pair as usual

D It stores the value twice

💡 Hint

Look at the decision step in the concept_flow where key-value pairs lead to hash map usage.

Concept Snapshot

Hash Map vs Hash Set:
- Hash Map stores key-value pairs.
- Hash Set stores unique values only.
- Both use hashing for fast lookup.
- Hash Map returns value by key.
- Hash Set checks presence of value.
- Use hash map for mappings, hash set for uniqueness.

Full Transcript

This visual execution compares hash maps and hash sets. The flow starts by checking if data has key-value pairs. If yes, a hash map is used; otherwise, a hash set is used. The example inserts two items into each structure and searches for existing and non-existing keys or values. The hash map stores pairs like ("apple":3), while the hash set stores unique values like "apple". Searching in a hash map returns the associated value or 'Not Found'. Searching in a hash set returns True if present or False if not. Key moments clarify that hash sets do not store values associated with keys and that searching for missing items returns negative results. The quiz tests understanding of outputs at specific steps and the conceptual difference between the two structures. The snapshot summarizes the main differences and usage scenarios.