Topic 6 -Algorithms

Question 1

What are 3 key techniques for computational thinking?

Answer 1

• decomposition
• abstracton
• algorithmic thinking

Question 2

What is decomposition?

Answer 2

breaking a complex problem down into smaller problems and solving each one individually

Question 3

What is abstraction?

Answer 3

picking out the important bits of information from the problem, ignoring the specific details that dont matter

Question 4

What is alghorithmic thinking?

Answer 4

a logical way of getting from the problem to the solution

Question 5

What is an algorithm?

Answer 5

A set of instructions for solving a problem

Question 6

What does START do in pseudocode?

Answer 6

Marks the beginning of the pseudocode.
Example: START

Question 7

What does END do in pseudocode?

Answer 7

Marks the end of the pseudocode.
Example: END

Question 8

What does INPUT do in pseudocode?

Answer 8

Requests data from the user or another source (like a file)
Example: INPUT age

Question 9

What does OUTPUT do in pseudocode?

Answer 9

Displays information to the user.
Example: OUTPUT "Hello, World!"

Question 10

What does IF…THEN…ELSE do in pseudocode?

Answer 10

A conditional structure used to make decisions.
Example:
~~~
IF number > 10 THEN
OUTPUT “Greater than 10”
ELSE
OUTPUT “10 or less”
END IF
~~~

Question 11

What does WHILE…DO do in pseudocode?

Answer 11

A loop that repeats while a condition is true.
Example:
~~~
WHILE number > 0 DO
OUTPUT “Positive number”
number = number - 1
END WHILE
~~~

Question 12

What does FOR…TO do in pseudocode?

Answer 12

A loop that runs a specific number of times.
Example:

FOR i = 1 TO 10 DO
   OUTPUT i
END FOR

Question 13

What does REPEAT…UNTIL do in pseudocode?

Answer 13

Similar to WHILE, but it checks the condition after the loop, meaning the loop runs at least once.
Example:

REPEAT
   OUTPUT "Enter a number"
   INPUT number
UNTIL number > 0

Question 14

What does END IF do in pseudocode?

Answer 14

Marks the end of an IF statement
Example:

IF number > 10 THEN
   OUTPUT "Greater than 10"
ELSE
   OUTPUT "10 or less"
END IF

Question 15

What does RETURN do in pseudocode?

Answer 15

Returns a value from a function or procedure.
Example:
RETURN sum

Question 16

How is a start/stop represented in a flow chart?

Answer 16

A rounded rectangle and the beginning and the end of the algorithm

Question 17

How is a input/output represented in a flow chart?

Answer 17

Anything that is put into or displayed in the algorithm is shown as a parallelogram

Question 18

How is a process represented in a flow chart?

Answer 18

General instructions, processes and calculations are shown as normal rectangular boxes

Question 19

How is a decision represented in a flow chart?

Answer 19

Decisions, often a yes or no question is shown as a diamond box

Question 20

How is a subroutine represented in a flow chart?

Answer 20

They are like sub programs- referencing other flow diagrams- shown as a rectangle with a verticle line on both sides

Question 21

What connects each shape in a flowchart and show the direction to go?

Answer 21

Arrows

Question 22

What does a binary search do?

Answer 22

looks for items in an ordered list

Question 23

Whats the steps of binary search?

divide and conquer

Answer 23

• find the middle item (n+1)/2 and round down if needed
• compare it with the target:
• if it’s the target, you’re done
• if the target is smaller, repeat with the left half
• if the target is larger, repeat with the right half
• repeat steps until the item is found

Question 24

What does a linear search do?

Answer 24

look for items in an unordered list

Question 25

Whats the steps of linear search?

Answer 25

* look at the first item in the list. * check if it’s the target. * if not, move to the next item. * repeat until you find it

Question 26

What does bubble sort do?

Answer 26

compares pairs of items to sort an unordered list

Question 27

Whats the steps of bubble sort?

Answer 27

* look at the first two items in the list * if they are in the right order, don't do anything, if not, swap them * move onto the next pair and then repeat step 2 * repeat step 3 until the highest number bubbles to the end- this is called one pass * repeat steps 1 to 4 until there are no swaps in a pass

Question 28

What does a merge sort do?

Answer 28

splits the list apart then merges it back together

Question 29

Whats the steps of merge sort? | divide and conquer

Answer 29

* split the list in half * keeping splitting the sub-lists until there is only one item in each list * merge and order the sub-lists back together * keep on merging the sublists until you only have one list

Question 30

What is an insertion sort?

Answer 30

orders the items as it goes

Question 31

How does insertion sort work?

Answer 31

* llook at the second item * compare it to all the items before it and inset it into the right place * repeat step two for the third,fourth,fifth, ect until the last number in the list has been inserted into the correct place