For loop basics in Go - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to print numbers from 0 to 4.

Go

for [1] := 0; i < 5; i++ {
    fmt.Println(i)
}

Drag options to blanks, or click blank then click option'

Ai

Bj

Cx

Dn

Attempts:

3 left

💡 Hint

Common Mistakes

Using a variable name that doesn't match the condition or increment part.

Using a variable name not declared in the loop.

The variable i is commonly used as the loop counter in Go for loops.

2fill in blank

medium

Complete the code to sum numbers from 1 to 5.

Go

sum := 0
for i := 1; i <= [1]; i++ {
    sum += i
}
fmt.Println(sum)

Drag options to blanks, or click blank then click option'

A4

B10

C6

D5

Attempts:

3 left

💡 Hint

Common Mistakes

Using a limit less than 5, so the sum misses the last number.

Using a limit greater than 5, causing extra iterations.

The loop should run until i is less than or equal to 5 to include 5 in the sum.

3fill in blank

hard

Fix the error in the loop condition to print even numbers from 0 to 8.

Go

for i := 0; i [1] 10; i += 2 {
    fmt.Println(i)
}

Drag options to blanks, or click blank then click option'

A>

B<

C>=

D<=

Attempts:

3 left

💡 Hint

Common Mistakes

Using greater than operator causing the loop to never run.

Using greater than or equal causing no output.

The loop should continue while i is less than 10 to print numbers up to 8.

4fill in blank

hard

Fill both blanks to create a loop that prints numbers from 5 down to 1.

Go

for i := [1]; i [2] 0; i-- {
    fmt.Println(i)
}

Drag options to blanks, or click blank then click option'

A5

B0

C>

D<

Attempts:

3 left

💡 Hint

Common Mistakes

Using less than operator causing the loop to never run.

Starting at 0 instead of 5.

The loop starts at 5 and continues while i is greater than 0, decreasing by 1 each time.

5fill in blank

hard

Fill all three blanks to create a loop that prints squares of numbers from 1 to 3.

Go

for [1] := 1; [2] <= 3; [3]++ {
    fmt.Println(i * i)
}

Drag options to blanks, or click blank then click option'

Aj

Bi

Attempts:

3 left

💡 Hint

Common Mistakes

Using different variable names causing errors.

Using a variable not declared in the loop.

The loop variable i is used consistently in initialization, condition, and increment.

Practice

1. What does a for loop do in Go programming?

easy

A. Stops the program immediately

B. Imports a package

C. Defines a new variable

D. Repeats a block of code while a condition is true

Solution

1. Step 1: Understand the purpose of a for loop

   A for loop is used to repeat code multiple times based on a condition.

2. Step 2: Identify the correct description

   Only Repeats a block of code while a condition is true correctly describes repeating code while a condition is true.

3. Final Answer:

   Repeats a block of code while a condition is true -> Option D

4. Quick Check:

   For loop = Repeat code [OK]

Hint: For loops repeat code while condition is true [OK]

Common Mistakes:

• Thinking for loop stops program
• Confusing for loop with variable declaration
• Mixing for loop with import statements

2. Which of the following is the correct syntax for a basic for loop in Go?

easy

A. for i := 0; i < 5; i++ { }

B. for (i = 0; i < 5; i++) { }

C. for i in range(5) { }

D. loop i from 0 to 5 { }

Solution

1. Step 1: Recall Go for loop syntax

   Go uses for init; condition; post { } syntax without parentheses.

2. Step 2: Compare options

   for i := 0; i < 5; i++ { } matches Go syntax exactly. Options B, C, and D use other languages or invalid syntax.

3. Final Answer:

   for i := 0; i < 5; i++ { } -> Option A

4. Quick Check:

   Go for loop = for init; condition; post [OK]

Hint: Go for loops use semicolons, no parentheses [OK]

Common Mistakes:

• Using parentheses like in C or Java
• Using Python-style for-in loops
• Writing 'loop' instead of 'for'

3. What is the output of this Go code?

for i := 1; i <= 3; i++ {
    fmt.Print(i, " ")
}

medium

A. 1 2 3

B. 0 1 2 3

C. 1 2 3 4

D. Syntax error

Solution

1. Step 1: Analyze loop range and output

   The loop starts at i=1 and runs while i <= 3, so i takes values 1, 2, 3.

2. Step 2: Understand print output

   Each iteration prints i followed by a space, so output is "1 2 3 "

3. Final Answer:

   1 2 3 -> Option A

4. Quick Check:

   Loop prints 1 to 3 with spaces [OK]

Hint: Check loop start, end, and print inside loop [OK]

Common Mistakes:

• Starting loop at 0 instead of 1
• Including extra number beyond 3
• Confusing print with println

4. Identify the error in this Go for loop:

for i := 0; i < 5 i++ {
    fmt.Println(i)
}

medium

A. Using := instead of = for i

B. Missing semicolon between condition and post statement

C. Using parentheses around for loop

D. Missing curly braces

Solution

1. Step 1: Check for loop syntax parts

   Go requires semicolons between init, condition, and post parts in for loops.

2. Step 2: Locate missing semicolon

   The code misses a semicolon between i < 5 and i++.

3. Final Answer:

   Missing semicolon between condition and post statement -> Option B

4. Quick Check:

   For loop parts separated by semicolons [OK]

Hint: Check semicolons between for loop parts [OK]

Common Mistakes:

• Omitting semicolons in for loop header
• Confusing := with = in loop variable
• Forgetting curly braces

5. How can you use a for loop in Go to sum all even numbers from 2 to 10 inclusive?

hard

A. for i := 2; i < 10; i += 2 { sum += i }

B. for i := 0; i <= 10; i += 2 { sum += i }

C. for i := 1; i <= 10; i++ { if i%2 == 0 { sum += i } }

D. for i := 2; i < 10; i++ { sum += i*2 }

Solution

1. Step 1: Understand the goal

   We want to add even numbers from 2 to 10 inclusive.

2. Step 2: Analyze each option

   for i := 2; i < 10; i += 2 { sum += i } increments by 2 starting at 2, but i < 10 so sums only 2+4+6+8 (misses 10).
   for i := 1; i <= 10; i++ { if i%2 == 0 { sum += i } } loops from 1 to 10, checks if number is even, then adds it. This is correct and clear.
   for i := 2; i < 10; i++ { sum += i*2 } incorrectly multiplies i by 2 and sums, which is wrong.
   for i := 0; i <= 10; i += 2 { sum += i } starts at 0, which includes 0 in sum, not desired.

3. Final Answer:

   for i := 1; i <= 10; i++ { if i%2 == 0 { sum += i } } -> Option C

4. Quick Check:

   Check even with modulo inside loop [OK]

Hint: Use modulo to check even numbers inside loop [OK]

Common Mistakes:

• Starting loop at 0 including unwanted numbers
• Multiplying instead of checking evenness
• Forgetting to check condition inside loop