UIL CS: Practice Resources & Tips

This is part of the UIL CS study series. See also:

• Number Systems
• Java Fundamentals
• Bitwise & Boolean
• Recursion & Loops
• OOP & Generics
• Collections & Algorithms

Main topic list: https://www.uiltexas.org/files/academics/UILCS-JavaTopicList2526.pdf

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Tips for Success

• Practice tracing code line by line.
• Use small examples to test logic (especially for loops, recursion, and bitwise).
• Memorize operator precedence and common collection method behaviors.
• Work past problems from all packet levels (Invitational, District, Region, State).

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Other important subjects to know (UIL-relevant)

1. Integer division and modulo (VERY common traps)

• $7 / 2 == 3$
• $7 \% 2 == 1$
• $-7 / 2 == -3$ in Java (truncates toward $0$)
• $-7 \% 2 == -1$

2. Type casting + promotion

• char participates in arithmetic as an integer code point
• expressions with mixed types promote:
  • int + double -> double
• integer overflow wraps around in Java (two's complement)

Example:

int x = Integer.MAX_VALUE;
System.out.println(x + 1); // wraps to negative

3. String pitfalls

• == compares references, not contents
• use .equals(...)

String a = new String("hi");
String b = new String("hi");
System.out.println(a == b);        // false
System.out.println(a.equals(b));   // true

4. Arrays vs ArrayList

• arrays fixed size, .length
• ArrayList dynamic size, .size()

5. Common off-by-one errors in loops

$i < n$ vs $i <= n$ nested loops counting iterations is a frequent UIL question.

6. Recursion: must identify base case + number of calls

UIL often asks output and/or call depth.

7. Sorting/searching concepts

Know basics:

• linear search: $O(n)$
• binary search: $O(\log n)$ (requires sorted data)
• typical sorting: $O(n \log n)$

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Practice Materials

Official UIL Resources

https://www.uilexas.org/academics/page/2025-high-school-academic-study-materials

Practice Tests

https://www.cs.utexas.edu/~scottm/uil/2008/practice2008.pdf

https://www.uilexas.org/files/academics/1-CompSci_2017_District-Test.pdf

https://www.cs.utexas.edu/~scottm/uil/practiceMaterials.html

https://www.apluscompsci.com/aplus_Sample_Test_2.pdf