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Day 4 — switch case (Java & C++) / match case (Python)

DSA Partner Challenge | Week 1: Language Basics + Maths for DSA

📌 Topic of the Day

##notes: https://drive.google.com/file/d/1zICbYGLxtGIG28DUc229gbpiOFoua2bO/view?usp=sharing

switch / match case — keeping it light

When you have one variable and many possible values to check, switch/match is cleaner than a chain of if-else. Today we learn all three flavours.

🎥 Resource

Language Resource
☕ Java switch case Tutorial
🐍 Python Same video + match-case docs (Python 3.10+)
⚙️ C++ Same video — C++ switch is identical to Java's traditional syntax

🧠 What to Learn Today

Java — switch

switch (expression) {
    case value1:
        // code
        break;
    case value2:
        // code
        break;
    default:
        // fallback
        break;
}

Enhanced switch (Java 14+) — no break needed:

switch (day) {
    case 1 -> System.out.println("Monday");
    case 2 -> System.out.println("Tuesday");
    default -> System.out.println("Other");
}

Key rules:

  • break is required in traditional switch — without it, execution falls into the next case
  • default is like else — runs when nothing matches
  • Supported types: int, char, String (Java 7+), byte, short, enum
  • NOT supported: long, double, float, boolean

Python — match / case (Python 3.10+)

match expression:
    case value1:
        # code
    case value2:
        # code
    case _:         # _ is the wildcard / default
        # fallback

Group cases with | (OR):

match month:
    case 4 | 6 | 9 | 11:
        print("30 days")
    case 2:
        print("28 or 29 days")
    case _:
        print("31 days")

Key rules:

  • NO break needed — Python match-case does not fall through
  • _ is the wildcard — acts as default
  • Works with Python 3.10+ only
  • Supports structural pattern matching (more powerful than Java's switch)

Before Python 3.10 — use a dict:

days = {1: "Monday", 2: "Tuesday", 3: "Wednesday"}
print(days.get(3, "Invalid"))   # Wednesday

C++ — switch

Same as Java's traditional switch:

switch (x) {
    case 1:
        cout << "One";
        break;
    case 2:
        cout << "Two";
        break;
    default:
        cout << "Other";
        break;
}

Key differences from Java:

  • No String support in C++ switch — use if-else for strings
  • Only integer types: int, char, short, long, long long, enum
  • C++17 added [[fallthrough]] attribute for intentional fall-through

Quick Comparison

Feature Java switch Python match C++ switch
Default default: case _: default:
Fall-through Yes — needs break No (auto-isolated) Yes — needs break
String support Yes (Java 7+) Yes No
OR in cases case 1: case 2: case 1 | 2: case 1: case 2:
Pattern matching Limited Full structural No

💻 Practice Questions

Solve in your language. Push solutions to your fork.

1. Perimeter of Rectangle

Formula: 2 × (length + breadth)

2. Perimeter of Square

Formula: 4 × side

3. Perimeter of Rhombus

Formula: 4 × side

4. Volume of Prism

Formula: base area × height

5. Volume of Cylinder

Formula: π × r² × h

6. Volume of Sphere

Formula: (4/3) × π × r³

7. Volume of Pyramid

Formula: (1/3) × base area × height

8. Curved Surface Area of Cylinder

Formula: 2 × π × r × h

9. Total Surface Area of Cube

Formula: 6 × side²

10. Fibonacci Series up to n numbers

0, 1, 1, 2, 3, 5, 8, 13, 21 ... Each number = sum of previous two

11. Subtract the Product and Sum of Digits of an Integer

Given: 234 Product of digits: 2 × 3 × 4 = 24 Sum of digits: 2 + 3 + 4 = 9 Answer: 24 - 9 = 15

✅ Checklist Before You Sleep

  • I know the basic switch syntax in Java and C++
  • I understand fall-through and why break is needed
  • I know which types are supported in switch (Java/C++)
  • I know how Python match-case is different from switch
  • I know _ is the wildcard/default in Python
  • I can use | to group cases in Python match-case
  • Solved at least 7 of the 11 practice questions

💬 Community

Stuck on any question? Drop the number in the community.

Solved all 11? Drop a 🔥 in the community.

Next up → Day 5: Functions & Methods — writing reusable code