Pattern_Analysis_Consolidated

Computational Thinking: Comprehensive Pattern Analysis & Solutions

Complete Qualifier Prep Guide - All 12 Weeks

Exam in 6 hours. Lock in. No distractions.

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🎯 MASTER PATTERN CHEAT SHEET

Week 1-4: HIGH WEIGHT in Qualifier (80%+)

Pattern 1: Datasets You MUST Know

Dataset	Columns
Words	Card#, Word, Part of Speech, Letter Count
Scores	Name, Subject, Marks, Gender, City, DOB
Library	Book, Author, Genre, Year, Language
Shopping Bills	Shop, Customer, Item, Price, Category
Olympics	Country, Gold, Silver, Bronze

Pattern 2: The Standard Loop

Step 1: Arrange cards in Pile 1
Step 2: Initialize variables (A=0, B=0, etc.)
Step 3: If Pile 1 is empty, STOP and go to final step
Step 4: Read top card from Pile 1
Step 5: If <condition> then <action>
Step 6: Move card to Pile 2, repeat from Step 3
Step 7: Final output calculation

Pattern 3: Accumulator Patterns

Pattern	Code	Use Case
Counter	A = A + 1	Counting items
Accumulator	A = A + X.Value	Summing values
Average	Result = Sum / Count	A/B at end
Max Finder	if X > Max then Max = X	Finding maximum
Flag/Existence	A = 1 (NOT A = A+1)	“Did it exist?”

Pattern 4: The “Reset Bug” Trap

Buggy: Repeat from Step 2 (where Step 2 sets count = 0) Fixed: Repeat from Step 3 (check empty, not reinitialize)

Why It’s Wrong: Every iteration resets the counter to 0!

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Logical Operators

Pattern 5: AND / OR / NOT

Expression	True When…
A and B	BOTH true
A or B	AT LEAST ONE true
not A	A is false

Example:

if (Shop == "SV Stores" and Price > 500)

Only counts if BOTH conditions are met.

Pattern 6: De Morgan’s Laws

$\neg (A\wedge B)\equiv \neg A\vee \neg B$ $\neg (A\vee B)\equiv \neg A\wedge \neg B$

English:

• NOT (A and B) = (NOT A) or (NOT B)
• NOT (A or B) = (NOT A) and (NOT B)

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Counter Types

Pattern 7: Simple Counter

count = count + 1

Increments by 1 each time condition is met.

Pattern 8: Distinct Counter (Flag Pattern)

if (Shop == "SV Stores") then A = 1
if (Shop == "Big Bazaar") then B = 1
if (Shop == "Sun General") then C = 1
X = A + B + C

Result = Number of distinct shops visited. Key: Using = 1, NOT = A + 1.

Pattern 9: Comparison Counter

if (X.Value > Y.Value) then A = A + 1
if (X.Value == Y.Value) then B = B + 1

Counts pairs based on comparison.

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Procedure Patterns

Pattern 10: Return True/False Procedures

procedure verifyPair(X, Y):
    if (X.Genre != Y.Genre and X.Author == Y.Author):
        return True
    else:
        return False

Pattern 11: Comparison Function

procedure compareSomething(A, B):
    if A > B:
        return -1
    else:
        return 1

Trap: Carefully note argument order (A, B) vs (B, A).

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Data Sanity Checks

Pattern 12: Data Type Errors

Column	Expected Type	Error Examples
Card Number	Integer	”One”, “1.5”, text
Letter Count	Positive Integer	-5, 0, decimal
Part of Speech	Noun/Verb/etc.	”Unknown”, number
Year	4-digit Integer	”Twenty Twenty”, 20.20

Pattern 13: Invalid Values

• Letter count cannot be negative or zero.
• Year cannot be in the future (if data is from past).
• Price cannot be negative.

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Code Tracing Tips

Pattern 14: Manual Dry Run

1. Draw a table with columns: Iteration, Card Data, Variable Values.
2. Process one card at a time.
3. Update ALL variables after each step.

Pattern 15: Nested IF = AND

if A:
    if B:
        action

Equivalent to: if (A and B): action

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Week 5-8: Advanced Patterns

Pattern 16: Double Loop (Pairs)

for each X in Table 1:
    for each Y in Table 2:
        if (condition on X and Y):
            count = count + 1

Note: This counts ALL pairs, including (A,B) and (B,A) separately.

Pattern 17: Same Author/Same Year

if (X.Author == Y.Author and X.Year == Y.Year):
    ...

Groups books by author-year combination.

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Week 9-12: Flowcharts & Algorithms

Pattern 18: Flowchart Symbols

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

Pattern 19: Searching Algorithms

• Linear Search: Check one by one. O(n).
• Binary Search: Requires sorted data. O(log n).

Pattern 20: Sorting Algorithms

• Bubble Sort: Compare adjacent, swap.
• Selection Sort: Find min, put at front.
• Insertion Sort: Insert into sorted portion.

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🚨 TOP 10 EXAM TRAPS

1. Reset Bug: Repeat from Step 2 when Step 2 initializes variables.
2. Count vs Flag: A = A + 1 (count) vs A = 1 (existence).
3. Argument Order: compare(A, B) vs compare(B, A) → Different results!
4. AND vs OR: A and B is stricter than A or B.
5. Nested IF: Same as AND, not OR.
6. Pair Counting: (A,B) and (B,A) count as 2 pairs.
7. Empty Pile Check: Must be at START of loop, not end.
8. Data Types: “One” is NOT an integer.
9. Letter Count Zero: Words MUST have ≥1 letter.
10. Double Loop Output: If comparing pairs, watch for duplicates.

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⚡ QUICK FORMULA REFERENCE

Average: $\frac{\text{Sum}}{\text{Count}}$

Counting: Increment by 1 when condition met.

Distinct Count: Use flags (0 or 1), sum at end.

Max/Min Finding:

Max = 0
for each X:
    if X.Value > Max:
        Max = X.Value

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You got this, dawg. Time to execute. 🔥