Nested conditional statements in C++ - Mini Project: Build & Apply

Nested Conditional Statements

📖 Scenario: You are creating a simple program to help a store clerk decide discounts based on customer membership and purchase amount.

🎯 Goal: Build a program that uses nested if statements to check if a customer is a member and then check their purchase amount to decide the discount.

📋 What You'll Learn

Create a variable isMember of type bool with value true or false

Create a variable purchaseAmount of type double with a specific value

Use nested if statements to check isMember and then purchaseAmount

Print the correct discount message based on conditions

💡 Why This Matters

🌍 Real World

Stores often give discounts based on membership and purchase amount. This program mimics that decision process.

💼 Career

Understanding nested conditions is important for writing clear decision-making code in many software jobs.

1

Create membership and purchase amount variables

Create a bool variable called isMember and set it to true. Create a double variable called purchaseAmount and set it to 120.0.

C++

// Your code here

Hint

Use bool for true/false and double for decimal numbers.

2

Add a discount threshold variable

Create a double variable called discountThreshold and set it to 100.0.

C++

bool isMember = true;
double purchaseAmount = 120.0;
// Your code here

Hint

This variable will help decide if the purchase amount qualifies for a discount.

3

Write nested if statements to check membership and purchase amount

Write nested if statements: first check if isMember is true. Inside it, check if purchaseAmount is greater than discountThreshold. If both are true, set a string variable discountMessage to "You get a 20% discount!". Otherwise, set discountMessage to "No discount available.". If isMember is false, set discountMessage to "Join our membership for discounts!".

C++

bool isMember = true;
double purchaseAmount = 120.0;
double discountThreshold = 100.0;
// Your code here

Hint

Remember to include #include <string> at the top to use std::string.

4

Print the discount message

Write a std::cout statement to print the discountMessage variable.

C++

bool isMember = true;
double purchaseAmount = 120.0;
double discountThreshold = 100.0;
#include 
#include 

std::string discountMessage;

if (isMember) {
    if (purchaseAmount > discountThreshold) {
        discountMessage = "You get a 20% discount!";
    } else {
        discountMessage = "No discount available.";
    }
} else {
    discountMessage = "Join our membership for discounts!";
}

// Your code here

Hint

Use std::cout << discountMessage << std::endl; to print the message.

Practice

1.

What does a nested conditional statement mean in C++?

easy

A. A loop inside a function

B. An if or else inside another if or else

C. A variable declared inside a function

D. A function calling itself

Solution

1. Step 1: Understand the meaning of nested conditionals

   Nested conditionals mean placing one if or else inside another to check multiple conditions step-by-step.

2. Step 2: Match the definition to the options

   An if or else inside another if or else correctly describes this as an if or else inside another if or else.

3. Final Answer:

   An if or else inside another if or else -> Option B

4. Quick Check:

   Nested conditional = if inside if [OK]

Hint: Look for condition inside another condition [OK]

Common Mistakes:

• Confusing nested conditionals with loops
• Thinking nested means multiple variables
• Mixing nested conditionals with recursion

2.

Which of the following is the correct syntax for a nested if statement in C++?

if (x > 0) {
    if (y < 10) {
        // code
    }
}

easy

A. if (x > 0) { if (y < 10) { // code } }

B. if (x > 0) if (y < 10) // code

C. if (x > 0) else if (y < 10) { // code }

D. if (x > 0) { else if (y < 10) { // code } }

Solution

1. Step 1: Check proper use of braces in nested if

   Correct nested if requires braces around inner if block inside outer if.

2. Step 2: Identify correct syntax option

   if (x > 0) { if (y < 10) { // code } } shows braces properly enclosing the inner if inside the outer if, which is correct syntax.

3. Final Answer:

   if (x > 0) { if (y < 10) { // code } } -> Option A

4. Quick Check:

   Braces around nested if blocks = correct syntax [OK]

Hint: Use braces {} to group nested if blocks [OK]

Common Mistakes:

• Missing braces causing syntax errors
• Using else if incorrectly inside nested if
• Placing else without matching if

3.

What is the output of the following C++ code?

int x = 5, y = 8;
if (x > 0) {
    if (y < 10) {
        std::cout << "A";
    } else {
        std::cout << "B";
    }
} else {
    std::cout << "C";
}

medium

A. No output

B. B

C. A

D. C

Solution

1. Step 1: Evaluate outer if condition

   Since x = 5 which is greater than 0, the outer if condition is true, so we enter the first block.

2. Step 2: Evaluate inner if condition

   Inside the outer block, y = 8 which is less than 10, so the inner if condition is true and prints "A".

3. Final Answer:

   A -> Option C

4. Quick Check:

   Both conditions true, print "A" [OK]

Hint: Check outer condition first, then inner [OK]

Common Mistakes:

• Ignoring inner condition and printing wrong letter
• Confusing else blocks
• Assuming else runs when outer if is true

4.

Find the error in this nested conditional code:

int a = 3;
if (a > 0)
    if (a < 5)
        std::cout << "Yes";
    else
        std::cout << "No";
else
    std::cout << "Maybe";

medium

A. Missing braces cause else to pair with wrong if

B. Syntax error: missing semicolon after if

C. Variable a is not declared

D. No error, code runs fine

Solution

1. Step 1: Analyze the indentation and else pairing

   Without braces, the else pairs with the nearest if, which can cause confusion in nested ifs.

2. Step 2: Identify the problem caused by missing braces

   Here, the else pairs with the inner if, not the outer, which may not be intended and causes logic errors.

3. Final Answer:

   Missing braces cause else to pair with wrong if -> Option A

4. Quick Check:

   Braces needed to avoid else ambiguity [OK]

Hint: Always use braces to avoid else ambiguity [OK]

Common Mistakes:

• Assuming else pairs with outer if
• Ignoring indentation does not affect pairing
• Thinking semicolon missing causes error

5.

Consider this code snippet:

int score = 85;
if (score >= 90) {
    std::cout << "Grade A";
} else {
    if (score >= 80) {
        std::cout << "Grade B";
    } else {
        std::cout << "Grade C";
    }
}

How can you rewrite this nested conditional using else if to improve clarity?

hard

A. if (score >= 90) { std::cout << "Grade A"; } else if (score < 80) { std::cout << "Grade C"; } else { std::cout << "Grade B"; }

B. if (score >= 90) { std::cout << "Grade A"; } if (score >= 80) { std::cout << "Grade B"; } else { std::cout << "Grade C"; }

C. if (score >= 90) { std::cout << "Grade A"; } else { std::cout << "Grade B"; } else { std::cout << "Grade C"; }

D. if (score >= 90) { std::cout << "Grade A"; } else if (score >= 80) { std::cout << "Grade B"; } else { std::cout << "Grade C"; }

Solution

1. Step 1: Understand nested if-else structure

   The original code uses an if inside an else to check score ranges.

2. Step 2: Rewrite using else if for clarity

   Using else if combines the conditions in a clear chain, avoiding deep nesting.

3. Final Answer:

   if (score >= 90) { std::cout << "Grade A"; } else if (score >= 80) { std::cout << "Grade B"; } else { std::cout << "Grade C"; } -> Option D

4. Quick Check:

   Use else if to flatten nested conditionals [OK]

Hint: Use else if to avoid nested if inside else [OK]

Common Mistakes:

• Using multiple ifs without else causing multiple outputs
• Placing else without matching if
• Incorrect order of conditions