Why hash tables enable O(1) lookup in Data Structures Theory - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the sentence to explain how hash tables find data quickly.

Data Structures Theory

Hash tables use a [1] function to find the storage location of data.

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Ahash

Bfilter

Csearch

Dsorting

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing 'sorting' because it relates to order, but hash tables don't sort data.

Choosing 'search' which is a general term but not the specific function used.

The hash function converts a key into an index, allowing quick access to data.

2fill in blank

medium

Complete the sentence to describe the average time complexity of hash table lookup.

Data Structures Theory

Hash tables provide an average lookup time complexity of [1].

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AO(n)

BO(1)

CO(log n)

DO(n log n)

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing O(n) which means time grows linearly with data size.

Choosing O(log n) which is typical for binary search trees, not hash tables.

Hash tables allow data to be found in constant time, which is O(1) on average.

3fill in blank

hard

Fix the error in the explanation about hash table collisions.

Data Structures Theory

When two keys hash to the same index, it is called a [1].

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Amapping

Bsorting

Ccollision

Dsearch

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing 'mapping' which is a general term for key to value association.

Choosing 'sorting' which is unrelated to hash table collisions.

A collision happens when different keys produce the same hash index.

4fill in blank

hard

Fill both blanks to explain how hash tables handle collisions.

Data Structures Theory

Hash tables handle collisions using [1] or [2] methods.

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Achaining

Bsorting

Copen addressing

Dindexing

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing 'sorting' which is unrelated to collision handling.

Choosing 'indexing' which is a general term for locating data.

Two common methods to handle collisions are chaining (using linked lists) and open addressing (finding another open slot).

5fill in blank

hard

Fill all three blanks to complete the explanation of why hash tables have O(1) lookup.

Data Structures Theory

The [1] function converts keys to [2] which point to [3] in the table.

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Ahash

Bindexes

Clocations

Dsearch

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up 'search' with 'hash' function.

Confusing 'indexes' with 'locations' or vice versa.

The hash function creates indexes that point to locations where data is stored, enabling fast lookup.