Why Arrays Exist and What Problem They Solve in DSA C - Test Your Knowledge

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare an array of 5 integers.

DSA C

int numbers[[1]];

Drag options to blanks, or click blank then click option'

A10

B5

C0

D1

Attempts:

3 left

💡 Hint

Common Mistakes

Using zero as the size, which creates an empty array.

Forgetting to specify the size.

The number inside the brackets specifies the size of the array. Here, 5 means the array can hold 5 integers.

2fill in blank

medium

Complete the code to access the third element of the array named 'data'.

DSA C

int value = data[1];

Drag options to blanks, or click blank then click option'

A[2]

B[1]

C[3]

D[0]

Attempts:

3 left

💡 Hint

Common Mistakes

Using index 3 for the third element, which is actually the fourth element.

Using index 1 which is the second element.

Array indexing starts at 0, so the third element is at index 2.

3fill in blank

hard

Fix the error in the code to correctly initialize an array with values 1, 2, 3.

DSA C

int arr[3] = [1]1, 2, 3[2];

Drag options to blanks, or click blank then click option'

A{

B[

C(

D}

Attempts:

3 left

💡 Hint

Common Mistakes

Using parentheses or square brackets instead of curly braces.

Forgetting to close the initializer with a brace.

Arrays in C are initialized using curly braces { } around the values.

4fill in blank

hard

Fill both blanks to create a loop that prints all elements of an array 'arr' of size 4.

DSA C

for(int i = 0; i [1] 4; i[2]) {
    printf("%d\n", arr[i]);
}

Drag options to blanks, or click blank then click option'

A<

B<=

C++

D--

Attempts:

3 left

💡 Hint

Common Mistakes

Using <= 4 causes out-of-bounds access.

Using -- causes an infinite loop.

The loop runs while i is less than 4, and i is incremented by 1 each time using ++.

5fill in blank

hard

Fill all three blanks to declare an array 'scores', assign 10 to the first element, and print it.

DSA C

int scores[3];
scores[1] = [2];
printf("%d", scores[3]);

Drag options to blanks, or click blank then click option'

A[0]

B10

D[1]

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong indices like [1] instead of [0].

Forgetting to assign a value before printing.

Arrays use square brackets to access elements. The first element is at index 0. We assign 10 to scores[0] and print scores[0].

Practice

1. Why do arrays exist in programming languages like C?

easy

A. To store multiple values of the same type in a single variable

B. To store different types of data in one variable

C. To perform mathematical calculations automatically

D. To create functions that run faster

Solution

1. Step 1: Understand the purpose of arrays

   Arrays allow storing many values of the same type together, making data management easier.

2. Step 2: Compare with other options

   Options B, C, and D describe features unrelated to arrays' main purpose.

3. Final Answer:

   To store multiple values of the same type in a single variable -> Option A

4. Quick Check:

   Arrays store same-type values together = A [OK]

Hint: Arrays group same-type values for easy access [OK]

Common Mistakes:

• Thinking arrays store different data types
• Confusing arrays with functions
• Believing arrays perform calculations automatically

2. Which of the following is the correct way to declare an array of 5 integers in C?

easy

A. int arr[5];

B. int arr;

C. array arr[5];

D. int arr = 5;

Solution

1. Step 1: Recall C array declaration syntax

   In C, arrays are declared by specifying type, name, and size in square brackets.

2. Step 2: Check each option

   int arr[5]; matches correct syntax; others are invalid or incorrect.

3. Final Answer:

   int arr[5]; -> Option A

4. Quick Check:

   C arrays use type name[size] = D [OK]

Hint: Use type name[size] to declare arrays in C [OK]

Common Mistakes:

• Omitting size in declaration
• Using wrong keywords like 'array'
• Assigning size as a value instead of array length

3. What will be the output of the following C code?

int arr[3] = {10, 20, 30};
printf("%d", arr[1]);

medium

A. Compilation error

B. 10

C. 30

D. 20

Solution

1. Step 1: Understand array indexing in C

   Arrays start at index 0, so arr[0] = 10, arr[1] = 20, arr[2] = 30.

2. Step 2: Identify printed value

   The code prints arr[1], which is 20.

3. Final Answer:

   20 -> Option D

4. Quick Check:

   arr[1] = 20 printed = A [OK]

Hint: Remember arrays start at index 0 in C [OK]

Common Mistakes:

• Confusing index 1 with first element
• Expecting output 10 instead of 20
• Thinking code causes error

4. Identify the error in the following C code snippet:

int arr[3];
arr[3] = 50;

medium

A. Syntax error in declaration

B. Missing semicolon

C. Array index out of bounds error

D. No error, code is correct

Solution

1. Step 1: Check array size and indexing

   Array of size 3 has valid indices 0, 1, 2 only.

2. Step 2: Analyze assignment arr[3] = 50;

   Index 3 is outside valid range, causing out of bounds error.

3. Final Answer:

   Array index out of bounds error -> Option C

4. Quick Check:

   Index 3 invalid for size 3 array = B [OK]

Hint: Array indices go from 0 to size-1 [OK]

Common Mistakes:

• Assuming index 3 is valid
• Ignoring array bounds in assignment
• Thinking code compiles without issues

5. You want to store the daily temperatures for a week and calculate their average. Why is using an array a good solution here?

medium

A. Because arrays can store different data types like numbers and text together

B. Because arrays allow storing multiple temperature values in one place for easy access and calculation

C. Because arrays automatically calculate averages for stored values

D. Because arrays increase the speed of the program without extra code

Solution

1. Step 1: Understand the problem of storing multiple related values

   Storing daily temperatures requires holding several numbers together for easy processing.

2. Step 2: Identify why arrays help

   Arrays group same-type values in one variable, making access and calculations like average straightforward.

3. Step 3: Eliminate incorrect options

   Arrays do not calculate averages automatically, nor store mixed types or speed up code without logic.

4. Final Answer:

   Because arrays allow storing multiple temperature values in one place for easy access and calculation -> Option B

5. Quick Check:

   Arrays group values for easy processing = C [OK]

Hint: Arrays hold many values together for easy calculations [OK]

Common Mistakes:

• Thinking arrays do calculations automatically
• Believing arrays store mixed data types
• Assuming arrays speed up code without logic