Linear Search (AQA GCSE Computer Science)

Revision Note

Test yourself

What is a searching algorithm?

  • Searching algorithms are precise step-by-step instructions that a computer can follow to efficiently locate specific data in massive datasets

  • Two common searching algorithms are:

    • Binary search

    • Linear search

  • A linear search starts with the first value in a dataset and checks every value one at a time until all values have been checked

  • A linear search can be performed even if the values are not in order

Step

Instruction

1

Check the first value

2

IF it is the value you are looking for

  • STOP!

3

ELSE move to the next value and check

4

REPEAT UNTIL you have checked all values and not found the value you are looking for

Examiner Tip

You will not be asked to perform a linear search on a dataset in the exam, you will be expected to understand how to do it and know the advantages and disadvantages compared to a binary search

Worked Example

A linear search could be used instead of a binary search.

Describe the steps a linear search would follow when searching for a number that is not in the given list [2]

Answer

  • Starting with the first value

  • Checking all values in order

Guidance

  • Must cover idea of checking all value AND being done in order!

  • "Checks each value from the beginning to the end" implies order so would get both bullet point 1 & 2

A linear search in python

# Identify the dataset to search, the target value and set the initial flag
data = [5, 2, 8, 1, 9]
target = 11
found = False

# Loop through each element in the data
for index in range(0,len(data) - 1):
  
  # Check if the current element matches the target
  if data[index] == target:
    67
    # If found, output message
    found = True
    print("Target found")

#If the target is not found, output a message
if found is False:
  print("Target not found")

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James Woodhouse

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James graduated from the University of Sunderland with a degree in ICT and Computing education. He has over 14 years of experience both teaching and leading in Computer Science, specialising in teaching GCSE and A-level. James has held various leadership roles, including Head of Computer Science and coordinator positions for Key Stage 3 and Key Stage 4. James has a keen interest in networking security and technologies aimed at preventing security breaches.

Lucy Kirkham

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