Algorithm Cheat Sheet

Quick reference for the fundamentals of algorithmic thinking.

🎯 Key Differences at a Glance

Concept	Definition	Format	Best For
Algorithm	Step-by-step problem-solving procedure	Plain English, math, diagrams	Planning and understanding logic
Pseudocode	Structured code-like notation	Text with programming keywords	Writing before actual coding
Flowchart	Visual diagram of algorithm flow	Shapes and arrows	Visualizing complex decisions

📝 Algorithm Properties

Every valid algorithm must have:

• ✅ Finite - Must terminate after a finite number of steps
• ✅ Definite - Each step must be precise and unambiguous
• ✅ Input - Takes zero or more inputs
• ✅ Output - Produces at least one output
• ✅ Effective - Each operation must be doable in finite time

🔤 Pseudocode Keywords

Keyword	Usage	Example
BEGIN	Start of algorithm	BEGIN CalculateSum
END	End of algorithm	END
INPUT	Accept user input	INPUT number
OUTPUT/PRINT	Display result	PRINT result
IF/THEN/ELSE	Conditional logic	IF x > 0 THEN
FOR/DO	Counted loop	FOR i FROM 1 TO 10 DO
WHILE/DO	Conditional loop	WHILE x > 0 DO
REPEAT/UNTIL	Post-test loop	REPEAT ... UNTIL x = 0
RETURN	Return value	RETURN result

🎨 Flowchart Symbols

Symbol	Name	Purpose
	Oval	Start/End points
	Rectangle	Process/Action
	Diamond	Decision (Yes/No)
	Parallelogram	Input/Output
	Arrow	Flow direction

🔄 Common Patterns

Sequence Pattern

Step 1
Step 2
Step 3

Selection Pattern (IF-THEN-ELSE)

IF condition THEN
    action1
ELSE
    action2
END IF

Repetition Pattern (LOOP)

WHILE condition DO
    action
END WHILE

📊 Quick Decision Guide

Situation	Use This
Planning a new program	Start with Algorithm
Teaching someone logic	Use Pseudocode
Complex decision logic	Draw Flowchart
Ready to code	Convert Pseudocode to actual code
Debugging logic	Review Flowchart

💡 Memory Tricks

• Algorithm = A Logical Guide Of Rules In Timesteps Having Meaning
• Pseudocode = Pretend Structured English Using Decorated Operations Code Of Developers Expressed
• Flowchart = Follow Logical Operations With Chart Hierarchy And Reviewable Trails

🚦 Best Practices

Writing Algorithms

✅ Use clear, simple language
✅ Number steps sequentially
✅ Handle edge cases
❌ Avoid ambiguous terms
❌ Don't skip steps

Writing Pseudocode

✅ Use consistent indentation
✅ One statement per line
✅ Include meaningful variable names
❌ Don't use language-specific syntax
❌ Avoid complex nesting

Drawing Flowcharts

✅ Use standard symbols consistently
✅ Keep flow top-to-bottom, left-to-right
✅ Label decision branches clearly
❌ Don't cross lines unnecessarily
❌ Avoid overcrowding

🔗 Related Concepts

• Variables & Data Types - storing data in algorithms
• Conditionals - implementing IF-THEN-ELSE logic
• Loops - implementing repetition patterns
• Functions - organizing algorithms into reusable blocks

📱 Quick Reference Card

ALGORITHM  →  The PLAN (what to do)
PSEUDOCODE →  The BLUEPRINT (how to write it)
FLOWCHART  →  The MAP (how it looks)

Remember

Master these three forms, and you'll be able to tackle any programming problem!