cpp_002_if Statement in C++

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The if statement is one of the most fundamental and powerful constructs in C++ programming. It allows you to execute a block of code based on whether a condition evaluates to true. In this blog post, we will dive deep into how the if statement works, explore its syntax, and look at practical examples.

Basic Syntax

The syntax of an if statement in C++ is as follows:

if (condition) {
    // Code to execute if the condition is true
}

Here:

• condition is a logical expression that evaluates to either true or false.
• The block of code inside the curly braces {} runs only if the condition is true.

Example 1: Basic if Statement

Problem Description: You are given an integer x. Write a program that checks if x is greater than 5 and prints a message if the condition is true.

#include <iostream>

int main() {
    int x = 10;

    if (x > 5) {
        std::cout << "x is greater than 5" << std::endl;
    }

    return 0;
}

Output:

x is greater than 5

Here, the condition x > 5 evaluates to true, so the code inside the if block executes.

Adding an else Clause

The else clause allows you to specify a block of code to execute when the condition is false.

Problem Description: You are given an integer x. Write a program that checks if x is greater than 5. If it is, print "x is greater than 5"; otherwise, print "x is not greater than 5."

if (condition) {
    // Code to execute if the condition is true
} else {
    // Code to execute if the condition is false
}

Example 2: Using if-else

#include <iostream>

int main() {
    int x = 3;

    if (x > 5) {
        std::cout << "x is greater than 5" << std::endl;
    } else {
        std::cout << "x is not greater than 5" << std::endl;
    }

    return 0;
}

Output:

x is not greater than 5

Using else if for Multiple Conditions

When you need to check multiple conditions, you can use the else if statement.

if (condition1) {
    // Code to execute if condition1 is true
} else if (condition2) {
    // Code to execute if condition2 is true
} else {
    // Code to execute if none of the conditions are true
}

Example 3: Handling Multiple Conditions

Problem Description: Write a program to check if a given integer x is less than 10, equal to 10, or greater than 10, and print the appropriate message.

#include <iostream>

int main() {
    int x = 15;

    if (x < 10) {
        std::cout << "x is less than 10" << std::endl;
    } else if (x == 10) {
        std::cout << "x is equal to 10" << std::endl;
    } else {
        std::cout << "x is greater than 10" << std::endl;
    }

    return 0;
}

Output:

x is greater than 10

Nested if Statements

You can nest if statements to handle more complex scenarios.

Example 4: Nested if Statements

Problem Description: Write a program that checks if a number x is between 10 and 30, inclusive. Print a message if the condition is met.

#include <iostream>

int main() {
    int x = 20;

    if (x > 10) {
        if (x < 30) {
            std::cout << "x is between 10 and 30" << std::endl;
        }
    }

    return 0;
}

Using just one if statement condition

#include <iostream>

int main() {
    int x = 20;

    if (x > 10 && x < 30) {
        std::cout << "x is between 10 and 30" << std::endl;
    }

    return 0;
}

Output:

x is between 10 and 30

Common Errors

1. Missing Parentheses:

if x > 5 { // Error: Missing parentheses
    std::cout << "Error";
}

1. Confusing Assignment with Comparison:

if (x = 5) { // Error: Should be x == 5
    std::cout << "Assignment instead of comparison";
}

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Quiz: Solve This Challenge!

Problem: Write a program that checks if a given integer x:

1. Is divisible by both 3 and 5.
2. Is divisible by 3 only.
3. Is divisible by 5 only.
4. Is not divisible by either 3 or 5.

Print the appropriate message for each case.

Hint: Use nested if statements and logical operators.

Solution:

#include <iostream>

int main() {
    int x;
    std::cout << "Enter a number: ";
    std::cin >> x;

    if (x % 3 == 0 && x % 5 == 0) {
        std::cout << "x is divisible by both 3 and 5" << std::endl;
    } else if (x % 3 == 0) {
        std::cout << "x is divisible by 3 only" << std::endl;
    } else if (x % 5 == 0) {
        std::cout << "x is divisible by 5 only" << std::endl;
    } else {
        std::cout << "x is not divisible by either 3 or 5" << std::endl;
    }

    return 0;
}

"Remember, every if statement is like a tiny detective in your code, always on the lookout for the truth!"