Do–while loop in C++ - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of a simple do–while loop

What is the output of this C++ code using a do–while loop?

C++

int i = 1;
do {
    std::cout << i << " ";
    i++;
} while (i <= 3);

A 1 2

B 1 2 3

C 2 3

D No output

💡 Hint

Remember, do–while executes the loop body before checking the condition.

The loop prints i starting from 1, then increments i. It repeats while i is less or equal to 3, so it prints 1 2 3.

❓ Predict Output

intermediate

Do–while loop with condition false initially

What will this C++ program print?

C++

int x = 5;
do {
    std::cout << x << " ";
    x++;
} while (x < 5);

A 5

B No output

C 5 6 7 ... (infinite loop)

D 6

💡 Hint

The loop runs once before checking the condition.

Even though x < 5 is false at start, do–while runs once, printing 5, then stops.

🔧 Debug

advanced

Identify the error in this do–while loop

What error will this code cause?

C++

int count = 0;
do {
    std::cout << count << " ";
    count++;
} while (count < 3);

A SyntaxError: missing semicolon

B Runtime error: infinite loop

C No error, prints 0 1 2

D Compilation error: undeclared variable

💡 Hint

Check punctuation carefully in C++.

The line 'count++' is missing a semicolon, causing a syntax error.

❓ Predict Output

advanced

Counting down with do–while loop

What does this code print?

C++

int n = 3;
do {
    std::cout << n << " ";
    n--;
} while (n > 0);

A 3 2 1 0

B 1 2 3

C 3 2 1

D No output

💡 Hint

The loop runs while n is greater than zero.

Starts at 3, prints 3, then 2, then 1, stops before printing 0.

🧠 Conceptual

expert

Behavior difference between while and do–while loops

Which statement best describes the difference between a while loop and a do–while loop in C++?

A A while loop always executes its body at least once, while a do–while loop may not execute at all.

B Neither loop executes if the condition is false initially.

C Both loops always execute their bodies at least once.

D A do–while loop always executes its body at least once, while a while loop may not execute at all.

💡 Hint

Think about when the condition is checked in each loop.

A do–while loop checks the condition after running the body, so it runs at least once. A while loop checks before running, so it may skip the body.