For loop in C++ - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of a simple for loop with increment

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

C++

for (int i = 0; i < 5; i++) {
    std::cout << i << " ";
}

A 0 1 2 3 4

B 1 2 3 4 5

C 0 1 2 3 4 5

D 1 2 3 4

💡 Hint

Remember the loop starts at 0 and runs while i is less than 5.

The loop starts at 0 and increments by 1 until it reaches 4. It stops before i equals 5, so it prints 0 1 2 3 4.

❓ Predict Output

intermediate

For loop with decrement

What will be printed by this C++ code?

C++

for (int i = 5; i > 0; i--) {
    std::cout << i << " ";
}

A 4 3 2 1 0

B 5 4 3 2 1

C 5 4 3 2 1 0

D 6 5 4 3 2 1

💡 Hint

The loop starts at 5 and decreases until it is greater than 0.

The loop prints from 5 down to 1. It stops before i reaches 0.

🧠 Conceptual

advanced

Understanding loop variable scope

What is the value of variable i after this loop finishes?

C++

int i = 10;
for (int i = 0; i < 3; i++) {
    // loop body
}
// What is i here?

A 3

B 0

C 10

D Undefined behavior

💡 Hint

Consider the scope of the variable declared inside the for loop.

The i declared inside the loop is a new variable local to the loop. The outer i remains unchanged at 10.

❓ Predict Output

advanced

Nested for loops output

What is the output of this nested for loop code?

C++

for (int i = 1; i <= 2; i++) {
    for (int j = 1; j <= 3; j++) {
        std::cout << i * j << " ";
    }
}

A 1 2 3 2 4 6

B 1 2 3 1 2 3

C 1 2 3 3 6 9

D 2 4 6 4 8 12

💡 Hint

Multiply i and j for each iteration and print in order.

For i=1, j=1 to 3 prints 1 2 3. For i=2, j=1 to 3 prints 2 4 6. Combined output is 1 2 3 2 4 6.

❓ Predict Output

expert

For loop with continue and break

What is the output of this code?

C++

for (int i = 0; i < 6; i++) {
    if (i == 2) continue;
    if (i == 4) break;
    std::cout << i << " ";
}

A 0 1 2 3

B 0 1 2 3 4

C 0 1 3 4

D 0 1 3

💡 Hint

Remember that continue skips the current iteration and break stops the loop.

When i is 2, continue skips printing. When i is 4, break stops the loop. So printed values are 0,1,3.