Algorithmic Problem-Solving Guides: Writing Algorithms For Real-World Scenarios (Copy)
Writing Algorithms For Real-World Scenarios
What “Real-World Scenarios” Mean In Algorithm Questions
- Problems are wrapped in everyday situations:
- Schools, shops, hospitals, traffic systems, games, forms
- The examiner is not testing realism
- The examiner is testing whether you can:
- Extract logic
- Ignore irrelevant detail
- Design a clean algorithm
Core Examiner Rule (Do Not Forget)
- Story ≠ Logic
- Marks are awarded for:
- Correct inputs
- Correct processing
- Correct outputs
- Names, emotions, context words carry zero marks
The 6-Step Real-World Algorithm Design Method
Step 1: Strip The Story To Raw Logic
- Ignore:
- Names
- Background
- Reasons
- Keep only:
- Data
- Conditions
- Results
Example
Story
“A teacher enters marks for students to see how many passed.”
Logic Extracted
- Input: marks
- Condition: ≥ 50
- Output: count
Step 2: Convert Real-World Items Into Variables
| Real-World Item | Program Representation |
|---|---|
| Student | Loop iteration |
| Marks | INTEGER |
| Name | STRING |
| Days | Loop limit |
| Decision | IF / ELSE |
| Repetition | FOR / WHILE |
Step 3: Identify The Algorithm Pattern
Most real-world problems fit one of these patterns:
| Pattern | Typical Scenarios |
|---|---|
| Counting | Attendance, passes, failures |
| Accumulation | Sales totals, distance |
| Searching | ID lookup, keyword |
| Validation | Forms, passwords, PIN |
| Selection | Discounts, grading |
| Monitoring | Sensors, limits |
Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total A Grades, 7 Distinctions and 11 World Records For Educate A Change AS Level Computer Science Full Scale Course
Step 4: Choose Control Structures From Wording
| Wording In Scenario | Correct Structure |
|---|---|
| “Each / Every” | FOR |
| “Keep asking until” | REPEAT UNTIL |
| “While condition holds” | WHILE |
| “If eligible” | IF |
| “Otherwise” | ELSE |
Step 5: Decide Whether You Need Arrays
- Use arrays only if:
- Values must be stored
- Values used later
- Do not use arrays for simple one-pass logic
Step 6: Write Exam-Safe Pseudocode
- Clear
- Simple
- Fully explicit
- No assumptions
Worked Example 1: School Attendance System
Scenario
“A teacher records attendance for 30 students and counts how many are present.”
Logic Breakdown
- Input: 30 attendance values
- Process: count present
- Output: total present
Pseudocode
count ← 0
FOR i ← 1 TO 30
INPUT status
IF status = "P" THEN
count ← count + 1
ENDIF
NEXT i
OUTPUT count
Worked Example 2: Shop Discount Calculation
Scenario
“A shop gives a 15% discount if the bill is greater than 8000.”
Logic Breakdown
- Input: bill
- Process: conditional discount
- Output: final bill
Pseudocode
INPUT bill
IF bill > 8000 THEN
bill ← bill - (bill * 0.15)
ENDIF
OUTPUT bill
Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total A Grades, 7 Distinctions and 11 World Records For Educate A Change AS Level Computer Science Full Scale Course
Worked Example 3: Password Validation
Scenario
“A system asks for a password until it has at least 8 characters.”
Logic Breakdown
- Input: password
- Process: length validation
- Output: acceptance
Pseudocode
REPEAT
INPUT password
UNTIL LENGTH(password) >= 8
OUTPUT "Accepted"
Worked Example 4: Temperature Alert System
Scenario
“A machine records temperatures until a value above 70 is detected.”
Logic Breakdown
- Input: temperature
- Process: compare with limit
- Output: alert
Pseudocode
REPEAT
INPUT temp
UNTIL temp > 70
OUTPUT "Alert Triggered"
Worked Example 5: Bank Withdrawal Check
Scenario
“A withdrawal is allowed only if sufficient balance is available.”
Logic Breakdown
- Input: balance, amount
- Process: comparison
- Output: result message
Pseudocode
INPUT balance
INPUT amount
IF amount <= balance THEN
balance ← balance - amount
OUTPUT "Approved"
ELSE
OUTPUT "Declined"
ENDIF
Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total A Grades, 7 Distinctions and 11 World Records For Educate A Change AS Level Computer Science Full Scale Course
Worked Example 6: Traffic Speed Monitoring
Scenario
“A speed camera records speeds of 25 vehicles and counts how many exceed 90.”
Pseudocode
count ← 0
FOR i ← 1 TO 25
INPUT speed
IF speed > 90 THEN
count ← count + 1
ENDIF
NEXT i
OUTPUT count
Worked Example 7: Hospital Patient Temperature Check
Scenario
“A nurse records patient temperatures and stops when a temperature below 35 is found.”
Logic Breakdown
- Input: temperature
- Process: check lower limit
- Output: warning
Pseudocode
REPEAT
INPUT temp
UNTIL temp < 35
OUTPUT "Hypothermia Risk"
Common Real-World Algorithm Mistakes
Mistake 1: Coding The Story
- Writing names and descriptions inside logic
Mistake 2: Assuming Inputs
- Every value must be explicitly INPUT
Mistake 3: Wrong Loop Choice
- FOR used when repetition unknown
- WHILE used when FOR is clearer
Mistake 4: Missing Output
- Logic correct
- No OUTPUT → mark loss
Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total A Grades, 7 Distinctions and 11 World Records For Educate A Change AS Level Computer Science Full Scale Course
Examiner Checklist For Real-World Scenarios
- Have all inputs been identified?
- Is every real-world rule reflected in logic?
- Are control structures correct?
- Is the output clear and final?
- Is the solution simple and readable?
Exam-Ready Real-World Algorithm Template
<initialise variables>
FOR / WHILE / REPEAT
INPUT
PROCESS
END LOOP
OUTPUT
One-Line Rules To Memorise
- Ignore the story
- Extract the logic
- Match wording to structures
- Use simplest solution
- Clarity always wins marks