Programming Readiness: Simple Algorithms and Edge Cases

This module supports R2, R4, R5, and R6. All work here is formative. Pick Java or Python and stay with it.

Specification checklist

Traced/worked example

Set<Integer> seen = new HashSet<>();
for (int n : nums) {
    if (seen.contains(target - n)) return true;
    seen.add(n);
}
return false;

For {2, 3, 5} and target 5: 2 is stored; 3 finds 2 already in the set and returns true.

For {3} and target 6, 3 is not in the set yet, so 6 - 3 misses; then 3 is added. The method returns false. Adding before the check would treat 3 + 3 as a pair.

Anagrams: "rail safety" and "fairy tales" match once spaces are removed.

Practice

Guided: Write two tests for targetSum before implementing: one true pair, one case that must be false ([] or {3} with target 6).

Independent: Implement isAnagram (ignore spaces) and targetSumWithSet.

Java: Practice.java, PracticeTest.java

javac Practice.java PracticeTest.java && java PracticeTest

Python: practice.py

python3 practice.py

Common mistakes

• Counting spaces as letters.
• Adding to the seen-set before looking for the complement.
• Returning true because the target itself appears in the list.

Exit guidance

Complete the self-check and tests. Explain why {3} / target 6 is false in both the nested-loop and set solutions.

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