AS SSD Data Structures

Question 1

How would you store multiple pieces of data in one place?

Answer 1

We must use a data structure such as a list or an array.

Question 2

What must you do when you are declaring an array?

Answer 2

You must give it a name as well as specify the type of data the array is going to store.

Question 3

What is an array considered to be?

Answer 3

It is considered as being fixed length.

Question 4

What does it mean when an array is considered as being fixed length?

Answer 4

This means that when an array is declared, you must set space required for all expected data types.

Question 5

What is another word that could replace fixed length in relation to arrays?

Answer 5

It could also be referred to as static.

Question 6

How would you store more data in an array?

Answer 6

You would have to make another array.

Question 7

How can items be accessed in an array?

Answer 7

Items in an array can be accessed by using the index of the array.

Question 8

At what number do index numbers start counting?

Answer 8

They start counting at 0.

Question 9

What is the most common type of multi-dimensional array called?

Answer 9

It is called a 2D array. It is essentially an array of arrays.

Question 10

What does a 2D array consist of?

Answer 10

it consists of rows and columns. This means that a number of rows and columns have to be specified.

Question 11

How would you add data to a 2D array?

Answer 11

When adding data to this type of array, you must specify the row and column in which you want to store the data.

Question 12

How would you access items within a 2D array?

Answer 12

Data is accessed in a 2D array using the same index position notation as when data is added to the array.

Question 13

How is a list similar to an array?

Answer 13

It is similar to an array in that it stores data of the same type.

Question 14

How does a list differ from an array?

Answer 14

A list differs from an array as it is considered as being dynamic. This means that the size of the list can change after it has been created and populated.

Question 15

What do you need to specify when creating a list?

Answer 15

You need to specify the type of list which is being created.

Question 16

When can you add or remove data from a list?

Answer 16

You can either remove or add data to a list before or after it has been created.

Question 17

How would you access items in a list?

Answer 17

To access items in a list, you must use the index position of the item being used.

Question 18

How would you loop through every item in a list?

Answer 18

Use a for-each loop.

Question 19

What are the two different types of sorting algorithms used with a list or an array?

Answer 19

Insertion sort and Bubble sort.

Question 20

How does an insertions sort work?

Answer 20

An insertion sort will compare each value in turn, starting with the second value in the list. If the value is greater than the value to the left of it, then no values will change positions. Otherwise, if the value is smaller than the value to the left of it. Otherwise, if the value is smaller than the value to the left of it, then it will move one position to the right of it.

Question 21

How does a Bubble sort work?

Answer 21

A bubble sort algorithm is different in that the largest values “bubble up’ the list to get to the top.

Question 22

What rules does the Bubble sort algorithm follow?

Answer 22

It looks at the first number in the list and compares the current number with the next number. If the next number is smaller than the current number the two numbers swap around. If not then they don’t. Move to the second number in the list and make this the current number and compare it with the next number and check to see if it is smaller than the current number. After you have reached the end of the list, if any numbers were swapped, repeat all steps again.

Question 23

What are the two algorithms called that are used to search through lists and arrays?

Answer 23

Binary and Linear search.

Question 24

What must happen before the binary search can start?

Answer 24

The list or array must be sorted already.

Question 25

How does a binary search work?

Answer 25

A binary search operates by finding the midpoint of a list and checking it against the value to be searched for. If the search value is larger than the midpoint, then everything to the left of the midpoint is discarded. If the search value is smaller than the midpoint, then everything to the right of the midpoint is discarded.

Question 26

What happens if the list contains an even number of items?

Answer 26

Instead you would chose the value either to the left or right of the calculated midpoint. If there is no midpoint in the next search then the direction is chosen consistently to ensure that the search narrows down effectively.

Question 27

How does a linear search work?

Answer 27

First the search term must be identified and look at the first item in the list. If the current item is the same as the search term then the item has been found. If not then move onto the next item. Repeat until the last item in the list has been reached. It the search term has not been found then the search term is not in the list.

Question 28

What is an icomparable function?

Answer 28

It is a way to sort data in a list based on a specific criteria.