Return values in C++ - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to return the sum of two integers.

C++

int add(int a, int b) {
    return [1];
}

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

Aa * b

Ba - b

Cb - a

Da + b

Attempts:

3 left

💡 Hint

Common Mistakes

Using subtraction or multiplication instead of addition.

Returning one of the parameters alone.

The function should return the sum of a and b, which is 'a + b'.

2fill in blank

medium

Complete the code to return the length of a string.

C++

#include <string>

int getLength(const std::string& str) {
    return [1];
}

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

Astr.size()

Bstr.length

Cstr.count()

Dstr.length()

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'count()' which is not a string method.

Using 'length' without parentheses.

Both 'str.size()' and 'str.length()' return the length of the string.

3fill in blank

hard

Fix the error in the function to correctly return the maximum of two numbers.

C++

int max(int x, int y) {
    if (x > y) {
        return [1];
    } else {
        return y;
    }
}

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

Ax

Bx > y

Cy

Dy > x

Attempts:

3 left

💡 Hint

Common Mistakes

Returning y inside the if block.

Returning a boolean expression instead of a variable.

If x is greater than y, the function should return x.

4fill in blank

hard

Fill both blanks to create a function that returns true if a number is even.

C++

bool isEven(int num) {
    return num [1] 2 [2] 0;
}

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

A%

B==

C!=

D/

Attempts:

3 left

💡 Hint

Common Mistakes

Using '/' instead of '%'.

Using '!=' instead of '=='.

To check if a number is even, use the modulus operator '%' and compare the result to 0 with '=='.

5fill in blank

hard

Fill all three blanks to create a function that returns a new string with the first character capitalized.

C++

#include <string>
#include <cctype>

std::string capitalize(const std::string& s) {
    if (s.empty()) return s;
    std::string result = s;
    result[[1]] = std::toupper(s[[2]]);
    return [3];
}

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

A0

B1

Cresult

Ds

Attempts:

3 left

💡 Hint

Common Mistakes

Using index 1 instead of 0 for the first character.

Returning the original string 's' instead of the modified 'result'.

The first character is at index 0. We capitalize s[0] and assign it to result[0], then return result.

Practice

1. What does the return statement do in a C++ function?

easy

A. It sends a value back to the place where the function was called.

B. It prints a value to the screen.

C. It declares a new variable inside the function.

D. It ends the program immediately.

Solution

1. Step 1: Understand the purpose of return

   The return statement is used to send a value from a function back to the caller.

2. Step 2: Differentiate from other statements

   Printing to screen or declaring variables are different actions; return specifically sends a value back.

3. Final Answer:

   It sends a value back to the place where the function was called. -> Option A

4. Quick Check:

   Return sends value back [OK]

Hint: Remember: return sends value back to caller [OK]

Common Mistakes:

• Confusing return with printing output
• Thinking return declares variables
• Believing return ends the whole program

2. Which of the following is the correct syntax to return an integer value 5 from a function in C++?

easy

A. return = 5;

B. return(5)

C. return 5;

D. return: 5;

Solution

1. Step 1: Recall correct return syntax

   In C++, the correct way to return a value is return value; with a semicolon.

2. Step 2: Check each option

   return 5; uses return 5; which is correct. return(5) misses semicolon. Options C and D use invalid syntax.

3. Final Answer:

   return 5; -> Option C

4. Quick Check:

   Correct return syntax ends with semicolon [OK]

Hint: Use 'return value;' with semicolon [OK]

Common Mistakes:

• Omitting semicolon after return
• Using '=' with return
• Using colon ':' instead of semicolon

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

int add() {
  return 2 + 3;
}

int main() {
  int result = add();
  std::cout << result;
  return 0;
}

medium

A. 23

B. 5

C. 0

D. Compilation error

Solution

1. Step 1: Analyze the add() function

   The function returns the sum of 2 + 3, which is 5.

2. Step 2: Check main() output

   Main calls add(), stores 5 in result, then prints it using std::cout.

3. Final Answer:

   5 -> Option B

4. Quick Check:

   2 + 3 = 5 [OK]

Hint: Add inside return, then print result [OK]

Common Mistakes:

• Thinking return concatenates numbers
• Confusing return value with print output
• Expecting zero without calculation

4. Identify the error in this function and choose the correct fix:

int multiply(int a, int b) {
  a * b;
}

medium

A. Add return before a * b;

B. Change function return type to void

C. Add semicolon after function declaration

D. Replace a * b; with return a + b;

Solution

1. Step 1: Check function body

   The function calculates a * b; but does not return it.

2. Step 2: Fix missing return

   To return the product, add return before a * b;.

3. Final Answer:

   Add return before a * b; -> Option A

4. Quick Check:

   Function must return value if return type is int [OK]

Hint: Return the calculated value explicitly [OK]

Common Mistakes:

• Forgetting to use return statement
• Changing return type unnecessarily
• Confusing multiplication with addition

5. You want a function that returns the larger of two integers. Which of these implementations correctly returns the larger value?

hard

A. int max(int x, int y) { return; }

B. int max(int x, int y) { if (x > y) return y; else return x; }

C. int max(int x, int y) { return x + y; }

D. int max(int x, int y) { if (x > y) return x; else return y; }

Solution

1. Step 1: Understand the goal

   The function should return the larger of x and y.

2. Step 2: Check each option logic

   int max(int x, int y) { if (x > y) return x; else return y; } returns x if x > y, else y, which is correct. int max(int x, int y) { if (x > y) return y; else return x; } reverses logic. int max(int x, int y) { return x + y; } returns sum, not max. int max(int x, int y) { return; } returns nothing.

3. Final Answer:

   int max(int x, int y) { if (x > y) return x; else return y; } -> Option D

4. Quick Check:

   Return larger value using if-else [OK]

Hint: Return x if greater, else y [OK]

Common Mistakes:

• Swapping return values in if-else
• Returning sum instead of max
• Missing return value