Control Structures — Practice Tasks¶

All tasks must be solved in Go, Java, and Python.

Beginner Tasks¶

Task 1: Print all numbers from 1 to N. If divisible by 3, print "Fizz". If by 5, "Buzz". If by both, "FizzBuzz".

Task 2: Given a number N, determine if it's prime using a loop. - Optimization: Only check up to sqrt(N).

Task 3: Print a right triangle of stars:

*
**
***
****
*****

Task 4: Given an array of integers, find the maximum and minimum in a single pass.

Task 5: Implement a number guessing game. Computer picks random 1-100, user guesses, program says "higher"/"lower".

Intermediate Tasks¶

Task 6: Implement bubble sort using nested loops. Count comparisons and swaps.

Task 7: Given a string, count vowels, consonants, digits, and spaces using a single loop.

Task 8: Print Pascal's triangle (first N rows) using nested loops.

Task 9: Implement binary search using a while loop. Return index or -1.

Task 10: Given a 2D matrix, print it in spiral order using while loops with boundary tracking.

Advanced Tasks¶

Task 11: Implement a simple state machine that validates email format character by character. - States: START, LOCAL_PART, AT_SIGN, DOMAIN, DOT, EXTENSION

Task 12: Write a producer-consumer pattern with a bounded buffer. - Go: channels; Java: BlockingQueue; Python: asyncio.Queue

Task 13: Implement the Sieve of Eratosthenes to find all primes up to N. - Use nested loops with early termination.

Task 14: Implement power function pow(base, exp) using: - a) Loop: O(n) - b) Fast exponentiation (squaring): O(log n)

Task 15: Implement a retry mechanism with exponential backoff. - Max 5 retries, delay doubles each time (1s, 2s, 4s, 8s, 16s).

Benchmark Task¶

Compare loop performance: for vs for-each vs while.

Go¶

package main

import (
    "fmt"
    "time"
)

func main() {
    n := 100_000_000
    arr := make([]int, n)
    for i := range arr { arr[i] = i }

    // Classic for
    start := time.Now()
    sum := 0
    for i := 0; i < n; i++ { sum += arr[i] }
    fmt.Printf("for index: %v (sum=%d)\n", time.Since(start), sum)

    // Range-based
    start = time.Now()
    sum = 0
    for _, v := range arr { sum += v }
    fmt.Printf("for range: %v (sum=%d)\n", time.Since(start), sum)
}

Java¶

public class LoopBenchmark {
    public static void main(String[] args) {
        int n = 100_000_000;
        int[] arr = new int[n];
        for (int i = 0; i < n; i++) arr[i] = i;

        // Classic for
        long start = System.nanoTime();
        long sum = 0;
        for (int i = 0; i < n; i++) sum += arr[i];
        System.out.printf("for index: %.2f ms (sum=%d)%n", (System.nanoTime()-start)/1e6, sum);

        // Enhanced for
        start = System.nanoTime();
        sum = 0;
        for (int v : arr) sum += v;
        System.out.printf("for-each:  %.2f ms (sum=%d)%n", (System.nanoTime()-start)/1e6, sum);
    }
}

Python¶

import timeit

n = 10_000_000
arr = list(range(n))

def sum_for():
    s = 0
    for i in range(len(arr)):
        s += arr[i]
    return s

def sum_foreach():
    s = 0
    for v in arr:
        s += v
    return s

def sum_builtin():
    return sum(arr)

print(f"for index:  {timeit.timeit(sum_for, number=3)/3*1000:.1f} ms")
print(f"for-each:   {timeit.timeit(sum_foreach, number=3)/3*1000:.1f} ms")
print(f"sum():      {timeit.timeit(sum_builtin, number=3)/3*1000:.1f} ms")