Logical operators in C++ - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of combined logical operators

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

C++

#include <iostream>
int main() {
    bool a = true, b = false, c = true;
    std::cout << (a && b || c) << std::endl;
    return 0;
}

A 0

B 1

C Compilation error

D Runtime error

💡 Hint

Remember the precedence of && and || operators.

The expression (a && b || c) evaluates as (false || true) which is true (1).

❓ Predict Output

intermediate

Logical NOT operator effect

What will be printed by this C++ program?

C++

#include <iostream>
int main() {
    bool x = false;
    std::cout << (!x && x) << std::endl;
    return 0;
}

A 1

B Runtime error

C Compilation error

D 0

💡 Hint

Check how !x and x combine with &&.

(!x && x) means (true && false) which is false (0).

❓ Predict Output

advanced

Short-circuit evaluation in logical AND

What is the output of this C++ code snippet?

C++

#include <iostream>
int main() {
    int i = 0;
    bool result = (false && (++i > 0));
    std::cout << i << std::endl;
    return 0;
}

A 0

B 1

C Compilation error

D Runtime error

💡 Hint

Does ++i get executed when the first operand is false in &&?

Because false && anything short-circuits, ++i is not executed, so i remains 0.

❓ Predict Output

advanced

Logical OR with side effects

What will be the output of this C++ program?

C++

#include <iostream>
int main() {
    int x = 5;
    bool val = (x > 10 || ++x > 5);
    std::cout << x << std::endl;
    return 0;
}

A 6

B Compilation error

C 5

D Runtime error

💡 Hint

Check if ++x is evaluated when x > 10 is false.

Since x > 10 is false, ++x > 5 is evaluated, incrementing x to 6.

🧠 Conceptual

expert

Understanding logical operator precedence

Given the expression: true || false && false, which part is evaluated first in C++?

A true || false && false (evaluated left to right)

B true || false

C false && false

D The expression causes a syntax error

💡 Hint

Remember operator precedence: && has higher precedence than ||.

&& is evaluated before ||, so false && false is evaluated first.