Overall Score

Scoring 34/39 on my College Board CSA exam allows me to feel confident in my CompSci abilities. However, I recognize an area for improvement in my time management as I spent more time than optimal on certain tasks. This realization underscores the importance of refining my approach to ensure more efficient use of time during future exams. Despite this, I am confident in my computer science essential skills, and I believe with strategic time management adjustments, I can further enhance my overall performance in the future.

Understanding the Questions I Got Wrong

Question 15

Code:

public static void showMe(int arg) {
      if (arg < 10) {
          showMe(arg + 1);
      } else {
          System.out.print(arg + "");
      }
  }

Correct Output:

012345678910

Explanation of Code

The method showMe takes an integer argument arg. If arg is less than 10, it calls itself recursively with arg + 1. This recursion continues until arg becomes 10 or greater, at which point the else block is executed, printing the current value of arg without a newline character.

The recursion will go from 0 to 10, printing each value in sequence without a newline. This results in the output: 012345678910.

Reflection

The mistake might have occurred if you overlooked the recursive nature of the method and the fact that it prints each value before reaching the base case. It’s crucial to understand the flow of the code, especially in recursive functions.

Question 17

Code:

/* Precondition: num greater than 0 */
public static int doWhat(int num) {
    int var = 0;

    for (int loop = 1; loop <= num; loop = loop + 2) {
        var += loop;
    }

    return var;
}

Correct Output + Explanation of Code:

For doWhat(1), the loop runs once with loop equal to 1, and the sum is 1. For doWhat(5), the loop runs three times with loop equal to 1, 3, and 5, and the sum is 1 + 3 + 5 = 9. For doWhat(10), the loop runs five times with loop equal to 1, 3, 5, 7, and 9, and the sum is 1 + 3 + 5 + 7 + 9 = 25.

So, the output for the given method with different values of num would be:

  • doWhat(1) returns 1.
  • doWhat(5) returns 9.
  • doWhat(10) returns 25.

Reflection

This method takes an integer num as input and initializes a variable var to 0. It then iterates through a loop that starts from 1 and increments by 2 until it reaches or exceeds num. In each iteration, it adds the current value of loop to var. Finally, it returns the value of var. Therefore the correct answer is: D. “The sum of all odd integers between 1 and num, inclusive”

Question 18 Reflection

Code:

System.out.print(404 / 10 * 10 + 1);

Correct Output:

401

Explanation of Code

  1. Order of Operations (PEMDAS/BODMAS):

  2. Division (/) and multiplication (*) have the same precedence and are evaluated from left to right.

Execution Steps:

404 / 10: Division of 404 by 10 equals 40. 40 * 10: Multiplication of 40 by 10 equals 400. 400 + 1: Addition of 1 to 400 equals 401.

Reflection

I may have overlooked the order of operations PEMDAS.

P: Parentheses/Brackets E: Exponents/Orders M/D: Multiplication and Division (left to right) A/S: Addition and Subtraction (left to right)

Question 33 Reflection

Code Segment I

 int max = Integer.MIN_VALUE;
 for (int value : arr) {
     if (max < value) {
         max = value;
     }
 }

This code initializes max to the minimum integer value and iterates through the array, updating max whenever a larger value is encountered. This code correctly finds the maximum element.

Code Segment II

 int max = 0;
 boolean first = true;
 for (int value : arr) {
     if (first) {
         max = value;
         first = false;
     } else if (max < value) {
         max = value;
     }
}

This code also initializes max to 0 and uses a boolean flag (first) to handle the first iteration differently. It correctly finds the maximum element.

Code Segment III

 int max = arr[0];
 for (int k = 1; k < arr.length; k++) {
     if (max < arr[k]) {
         max = arr[k];
     }
 }

This code initializes max to the first element of the array and iterates from the second element onward, updating max when a larger element is found. This code also correctly finds the maximum element.

Conclusion

All three code segments correctly find the maximum element in the array, and any of them can be used for this purpose.

The correct response is:

E. I, II, and III

Question 37 Reflection

Code Segment I

for (int k = startIndex; k < words.length; k++) {
     result += words[k] + words[words.length - k - 1];
 }

This code uses a for loop to iterate through the array, concatenating pairs of elements from the array in reverse order. It correctly concatenates the elements.

Code Segment II

 int k = words.length - 1;
 while (k >= startIndex) {
     result += words[k];
     k--;
 }

This code initializes k to the last index of the array and uses a while loop to concatenate elements in reverse order. It correctly concatenates the elements.

Code Segment III

String[] temp = new String[words.length];
for (int k = 0; k <= words.length / 2; k++) {
     temp[k] = words[words.length - k - 1];
     temp[words.length - k - 1] = words[k];
 }
 for (int k = 0; k < temp.length - startIndex; k++) {
     result += temp[k];
 }

This code creates a temporary array, swaps elements to reverse their order, and then concatenates elements starting from the startIndex. While it works, it’s more complex than necessary for the given task.

Conclusion

Both Code Segment I and Code Segment II correctly implement the logic needed for the concatWords method. Code Segment III, while functional, is more complicated and involves unnecessary steps.

The correct response is:

D. I and II

Final Reflections

Question 15:

Looking back, I see that my mistake in this question stemmed from overlooking the recursive nature of the method. It’s clear now that the method prints each value before reaching the base case. This highlights the importance of fully grasping the flow of recursive functions, and I’ll make sure to pay closer attention to such details in the future.

Question 17:

Upon reflection, my understanding of the loop structure and the nature of the sum being odd integers was correct. Recognizing the importance of the loop iterating over odd numbers was key. This reinforces my understanding of loop structures and the significance of the problem’s constraints.

Question 18:

In hindsight, I realize that my mistake in this question was overlooking the order of operations (PEMDAS). It’s a reminder for me to always consider the sequence of operations to achieve the correct result. This experience has reinforced the importance of adhering to fundamental principles.

Question 33:

Reflecting on this question, I feel confident in recognizing the correct solutions and understanding their logic. It underscores the importance of understanding the order of operations and the correct application of code segments. This reinforces my confidence in problem-solving using different approaches.

Question 37:

My reflection on the concatenation problem reveals that while I correctly identified simpler solutions, there’s always room for improvement in code simplicity. Choosing straightforward and efficient solutions is a key aspect of effective coding, and I’ll continue striving for clarity in my code.

Additional Work - Recursive Functions and Algorithms

In this test, I noticed that I struggled with Recursive Functions and Algorithms, so I spent some more time on this subject

Recursive Function Example:

public class RecursiveExamples {

    // Recursive function to calculate the factorial of a number
    public static int factorial(int n) {
        if (n == 0 || n == 1) {
            return 1;
        } else {
            return n * factorial(n - 1);
        }
    }

    public static void main(String[] args) {
        // Testing the factorial function
        int result = factorial(5);
        System.out.println("Factorial of 5: " + result);
    }
}

In this example, the factorial function is implemented recursively to calculate the factorial of a number. The base case is when n is 0 or 1, in which case the function returns 1. Otherwise, it recursively calls itself with n - 1. This demonstrates the fundamental concept of recursion in calculating factorials.

Recursive Algorithm Example:

import java.util.Arrays;

public class RecursiveAlgorithm {

    // Recursive function to perform binary search on a sorted array
    public static int binarySearch(int[] arr, int target, int start, int end) {
        if (start > end) {
            return -1; // Element not found
        }

        int mid = start + (end - start) / 2;

        if (arr[mid] == target) {
            return mid; // Element found at mid index
        } else if (arr[mid] < target) {
            return binarySearch(arr, target, mid + 1, end); // Search in the right half
        } else {
            return binarySearch(arr, target, start, mid - 1); // Search in the left half
        }
    }

    public static void main(String[] args) {
        // Testing binary search on a sorted array
        int[] sortedArray = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
        int target = 7;

        int result = binarySearch(sortedArray, target, 0, sortedArray.length - 1);

        if (result != -1) {
            System.out.println("Element " + target + " found at index " + result);
        } else {
            System.out.println("Element " + target + " not found in the array.");
        }
    }
}

In this example, the binarySearch function is implemented using recursion to perform a binary search on a sorted array. The function takes the array, target element, and the start and end indices as parameters. It recursively divides the array in half based on the comparison with the target element until the element is found or the search space is exhausted. This demonstrates the use of recursion in a classic searching algorithm.