Function parameters in C++ - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of function with default parameters

What is the output of this C++ code?

C++

#include <iostream>
#include <string>
using namespace std;

void greet(string name = "Guest", int times = 1) {
    for (int i = 0; i < times; i++) {
        cout << "Hello, " << name << "!\n";
    }
}

int main() {
    greet();
    greet("Alice", 2);
    return 0;
}

A

Hello, Guest!
Hello, Guest!
Hello, Alice!
Hello, Alice!

B

Hello, Guest!
Hello, Alice!
Hello, Alice!

C

Hello, Guest!
Hello, Alice!

D

Hello, Alice!
Hello, Alice!

💡 Hint

Remember how default parameters work when no arguments are passed.

The function greet has default parameters: name = "Guest" and times = 1. When called without arguments, it prints "Hello, Guest!" once. When called with "Alice" and 2, it prints "Hello, Alice!" twice.

❓ Predict Output

intermediate

Output of function with pass-by-reference parameter

What is the output of this C++ code?

C++

#include <iostream>
using namespace std;

void addOne(int &num) {
    num += 1;
}

int main() {
    int a = 5;
    addOne(a);
    cout << a << endl;
    return 0;
}

A

5

B

Compilation error

C

6

D

Undefined behavior

💡 Hint

Think about how passing by reference affects the original variable.

The function addOne takes an integer reference and increments it. The original variable a is changed from 5 to 6, so the output is 6.

❓ Predict Output

advanced

Output of function with const reference parameter

What is the output of this C++ code?

C++

#include <iostream>
using namespace std;

void printValue(const int &val) {
    cout << val << endl;
}

int main() {
    int x = 10;
    printValue(x);
    return 0;
}

A

10

B

Compilation error

C

0

D

Undefined behavior

💡 Hint

Const references allow reading but not modifying the argument.

The function printValue takes a const reference to an int and prints it. The value of x is 10, so it prints 10.

❓ Predict Output

advanced

Output of function with pointer parameter

What is the output of this C++ code?

C++

#include <iostream>
using namespace std;

void setZero(int *ptr) {
    if (ptr) {
        *ptr = 0;
    }
}

int main() {
    int a = 5;
    setZero(&a);
    cout << a << endl;
    return 0;
}

A

0

B

5

C

Compilation error

D

Segmentation fault

💡 Hint

Pointers can be used to modify the value they point to.

The function setZero takes a pointer to int and sets the pointed value to 0. Since a is passed by address, its value changes to 0.

❓ Predict Output

expert

Output of overloaded functions with different parameter types

What is the output of this C++ code?

C++

#include <iostream>
using namespace std;

void print(int x) {
    cout << "int: " << x << endl;
}

void print(double x) {
    cout << "double: " << x << endl;
}

int main() {
    print(5);
    print(5.0);
    print('5');
    return 0;
}

A

int: 5
double: 5.0
int: 53

B

int: 5
double: 5
int: 5

C

int: 5
double: 5
Compilation error

D

int: 5
double: 5
int: 53

💡 Hint

Remember how char is promoted to int in function overloading.

The call print(5) matches print(int). The call print(5.0) matches print(double). The call print('5') passes a char, which is promoted to int with ASCII value 53, so print(int) is called printing 53.

Practice

1.

What is the purpose of function parameters in C++?

easy

A. To send data into functions so they can use it

B. To define the return type of a function

C. To declare variables inside the function body

D. To specify the function's name

Solution

1. Step 1: Understand function parameters

   Function parameters are variables listed in the function definition that receive values when the function is called.

2. Step 2: Identify their purpose

   They allow the function to work with different data each time it is called, making the function flexible and reusable.

3. Final Answer:

   To send data into functions so they can use it -> Option A

4. Quick Check:

   Function parameters = input data for functions [OK]

Hint: Parameters pass data into functions for reuse [OK]

Common Mistakes:

• Confusing parameters with return types
• Thinking parameters declare variables inside function body
• Believing parameters define function name

2.

Which of the following is the correct syntax to declare a function add that takes two int parameters a and b?

easy

A. int add(int a, int b);

B. int add(a int, b int);

C. int add(int a; int b);

D. int add(int a b);

Solution

1. Step 1: Recall correct parameter syntax

   In C++, parameters are declared as type name pairs separated by commas inside parentheses.

2. Step 2: Check each option

   int add(int a, int b); correctly uses int a, int b. Options A, B, and C have syntax errors like missing comma, wrong order, or semicolon.

3. Final Answer:

   int add(int a, int b); -> Option A

4. Quick Check:

   Parameters = type name, comma separated [OK]

Hint: Parameters need type and name, separated by commas [OK]

Common Mistakes:

• Swapping type and name order
• Using semicolons instead of commas
• Omitting commas between parameters

3.

What will be the output of the following code?

void greet(std::string name) {
    std::cout << "Hello, " << name << "!" << std::endl;
}

int main() {
    greet("Alice");
    return 0;
}

medium

A. Compilation error

B. Hello, name!

C. Hello, !

D. Hello, Alice!

Solution

1. Step 1: Understand function call with parameter

   The function greet takes a string parameter name and prints "Hello, " plus the value of name.

2. Step 2: Check the argument passed

   In main, greet is called with "Alice", so name becomes "Alice".

3. Final Answer:

   Hello, Alice! -> Option D

4. Quick Check:

   Parameter value replaces variable in output [OK]

Hint: Function prints parameter value passed in call [OK]

Common Mistakes:

• Thinking parameter name prints literally
• Expecting empty output if parameter unused
• Assuming syntax error due to string parameter

4.

Identify the error in this function declaration:

void printSum(int a, b) {
    std::cout << a + b << std::endl;
}

medium

A. Parameters should be inside square brackets

B. Missing type for parameter b

C. Function must return int

D. Function name is invalid

Solution

1. Step 1: Check parameter declarations

   Each parameter must have a type and a name. Here, b has no type specified.

2. Step 2: Identify correct syntax

   The correct declaration is void printSum(int a, int b). Missing type causes a syntax error.

3. Final Answer:

   Missing type for parameter b -> Option B

4. Quick Check:

   Every parameter needs a type [OK]

Hint: Each parameter must have a type before its name [OK]

Common Mistakes:

• Omitting type for second or later parameters
• Assuming return type must be int
• Using wrong brackets for parameters

5.

Consider this function that calculates the area of a rectangle:

double area(double width, double height) {
    return width * height;
}

How would you call this function to calculate the area of a rectangle with width 5.0 and height 3.0, and store the result in a variable result?

hard

A. double result = area(width=5.0, height=3.0);

B. double result = area(3.0, 5.0);

C. double result = area(5.0, 3.0);

D. double result = area(5, 3);

Solution

1. Step 1: Understand parameter order and types

   The function expects width first, then height, both as doubles.

2. Step 2: Check each call option

   double result = area(5.0, 3.0); passes 5.0 as width and 3.0 as height correctly. double result = area(3.0, 5.0); swaps them. double result = area(width=5.0, height=3.0); uses invalid named arguments (not supported in C++). double result = area(5, 3); passes ints which convert but less precise.

3. Final Answer:

   double result = area(5.0, 3.0); -> Option C

4. Quick Check:

   Call with correct order and types [OK]

Hint: Match argument order and types exactly [OK]

Common Mistakes:

• Swapping argument order
• Using named arguments (not valid in C++)
• Passing wrong types without conversion