Nested loop execution in C Sharp (C#) - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of nested loops with break

What is the output of the following C# code?

C Sharp (C#)

for (int i = 1; i <= 3; i++) {
    for (int j = 1; j <= 3; j++) {
        if (j == 2) break;
        Console.Write(i * j + " ");
    }
}

A 1 2 3 4 5 6

B 1 3 1 3 1 3

C 1 2 3

D 1 2 2 4 3 6

💡 Hint

Remember that 'break' exits the inner loop immediately when j equals 2.

The inner loop breaks when j == 2, so only j == 1 runs each time, printing i*1 (1, then 2, then 3).

❓ Predict Output

intermediate

Counting iterations in nested loops

How many times will the innermost statement execute in this code?

C Sharp (C#)

int count = 0;
for (int i = 0; i < 4; i++) {
    for (int j = i; j < 4; j++) {
        count++;
    }
}
Console.WriteLine(count);

A 8

B 16

C 6

D 10

💡 Hint

Count how many times the inner loop runs for each i.

For i=0, j runs 4 times; i=1, j runs 3 times; i=2, j runs 2 times; i=3, j runs 1 time. Total = 4+3+2+1=10.

🔧 Debug

advanced

Identify the error in nested loops

What error will this code produce when compiled or run?

C Sharp (C#)

for (int i = 0; i < 3; i++)
    for (int j = 0; j < 3; j++)
        Console.WriteLine(i + j);
    Console.WriteLine("Done");

A Prints sums nine times and then "Done" once

B Compilation error due to missing braces

C Runtime error: NullReferenceException

D No error, prints sums and then "Done" three times

💡 Hint

Check how indentation and braces affect which statements belong to loops.

The outer for loop body is the inner for statement (no braces needed for single statement). Inner for body is the WriteLine(i+j). "Done" executes once after both loops. Prints 9 sums then "Done".

📝 Syntax

advanced

Find the syntax error in nested loops

Which option contains the syntax error in nested loops?

C Sharp (C#)

for (int i = 0; i < 2; i++) {
    for (int j = 0; j < 2; j++)
        Console.WriteLine(i + j);
}

A

for (int i = 0; i < 2; i++)
    for (int j = 0; j < 2; j++)
        Console.WriteLine(i + j);

B

for (int i = 0; i < 2; i++) {
    for int j = 0; j < 2; j++) {
        Console.WriteLine(i + j);
    }
}

C

for (int i = 0; i < 2; i++) {
    for (int j = 0; j < 2; j++) {
        Console.WriteLine(i + j);
    }
}

D

for (int i = 0; i < 2; i++) {
    for (int j = 0; j < 2; j++)
        Console.WriteLine(i + j);
}

💡 Hint

Check the syntax of the inner for loop declaration.

Option B misses the opening parenthesis '(' after 'for' in the inner loop: 'for int j' instead of 'for (int j'.

🚀 Application

expert

Calculate sum of products in nested loops

What is the value of 'total' after running this code?

C Sharp (C#)

int total = 0;
for (int i = 1; i <= 3; i++) {
    for (int j = 1; j <= 3; j++) {
        if ((i + j) % 2 == 0) {
            total += i * j;
        }
    }
}
Console.WriteLine(total);

A 20

B 25

C 36

D 30

💡 Hint

Add products only when the sum of indices is even.

Pairs where (i+j) even: (1,1):1*1=1, (1,3):1*3=3, (2,2):2*2=4, (3,1):3*1=3, (3,3):3*3=9. Sum=1+3+4+3+9=20.