Loop execution flow in Go - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to print numbers from 1 to 5 using a for loop.

Go

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

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

A<

B>

C<=

D>=

Attempts:

3 left

💡 Hint

Common Mistakes

Using '<' will stop before printing 5.

Using '>' or '>=' will cause the loop not to run.

The loop should run while i is less than or equal to 5 to print numbers 1 through 5.

2fill in blank

medium

Complete the code to sum numbers from 1 to 10 using a for loop.

Go

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

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

A<

B<=

C>

D>=

Attempts:

3 left

💡 Hint

Common Mistakes

Using '<' excludes 10 from the sum.

Using '>' or '>=' will not run the loop correctly.

The loop must include 10, so the condition should be i <= 10.

3fill in blank

hard

Fix the error in the loop condition to print even numbers from 2 to 10.

Go

for i := 2; 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 '<' excludes 10 from printing.

Using '>' or '>=' will cause the loop not to run.

The loop should continue while i is less than or equal to 10 to include 10.

4fill in blank

hard

Fill both blanks to create a loop that prints numbers from 10 down to 1.

Go

for i := 10; i [1] 1; 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 '<=' will cause the loop to never run.

Using '++' will increase i and cause an infinite loop.

The loop should run while i is greater than or equal to 1, and decrement i each time using --.

5fill in blank

hard

Fill all three blanks to create a loop that prints only odd numbers from 1 to 9.

Go

for i := [1]; i [2] 9; i [3] {
    fmt.Println(i)
}

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

A1

B<=

Ci += 2

D0

Attempts:

3 left

💡 Hint

Common Mistakes

Starting at 0 will print even numbers.

Using '<' excludes 9 from printing.

Incrementing by 1 prints all numbers, not just odd.

The loop starts at 1, runs while i is less than or equal to 9, and increments i by 2 to get odd numbers.

Practice

1. What is the main purpose of a for loop in Go?

easy

A. To handle errors

B. To define a new variable

C. To repeat a block of code while a condition is true

D. To declare a function

Solution

1. Step 1: Understand the role of loops

   Loops are used to repeat actions multiple times based on a condition.

2. Step 2: Identify the purpose of for in Go

   In Go, the for loop is the only loop and repeats code while a condition holds true.

3. Final Answer:

   To repeat a block of code while a condition is true -> Option C

4. Quick Check:

   Loop = repeat code [OK]

Hint: Loops repeat code while condition true [OK]

Common Mistakes:

• Confusing loops with variable declarations
• Thinking loops handle errors
• Mixing loops with function declarations

2. Which of the following is the correct syntax for a basic for loop in Go that runs 3 times?

easy

A. for i := 0; i < 3; i++

B. for (i = 0; i < 3; i++) { }

C. for i = 0; i < 3; i++ { }

D. for i := 0; i < 3; i++ { }

Solution

1. Step 1: Check Go loop syntax

   Go requires initialization with :=, condition, and post statement inside parentheses without extra parentheses around the whole for.

2. Step 2: Validate each option

   for i := 0; i < 3; i++ { } uses correct syntax: for i := 0; i < 3; i++ { }. Options B and C have wrong parentheses or missing :=. for i := 0; i < 3; i++ misses braces.

3. Final Answer:

   for i := 0; i < 3; i++ { } -> Option D

4. Quick Check:

   Correct Go for loop syntax = for i := 0; i < 3; i++ { } [OK]

Hint: Use := for init, semicolons, braces for loop [OK]

Common Mistakes:

• Using parentheses like C/Java
• Missing := for variable declaration
• Omitting braces {}

3. What will be the output of this Go code?

for i := 1; i <= 3; i++ {
    if i == 2 {
        continue
    }
    fmt.Print(i)
}

medium

A. 13

B. 12

C. 123

D. 23

Solution

1. Step 1: Understand the loop and continue

   The loop runs i from 1 to 3. When i equals 2, continue skips printing.

2. Step 2: Trace output for each i

   i=1 prints '1', i=2 skips print, i=3 prints '3'. Output is '13'.

3. Final Answer:

   13 -> Option A

4. Quick Check:

   Continue skips i=2 print = 13 [OK]

Hint: Continue skips current iteration print [OK]

Common Mistakes:

• Assuming continue prints the skipped value
• Confusing continue with break
• Ignoring loop condition

4. Identify the error in this Go loop code:

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

medium

A. Missing braces {} around loop body

B. Incorrect loop condition

C. Variable i not declared

D. Using println instead of Println

Solution

1. Step 1: Check Go loop syntax rules

   Go requires braces {} to define the loop body even if it is one statement.

2. Step 2: Identify missing braces

   The code lacks braces around fmt.Println(i), causing a syntax error.

3. Final Answer:

   Missing braces {} around loop body -> Option A

4. Quick Check:

   Braces required for loop body [OK]

Hint: Always use braces {} for loop body [OK]

Common Mistakes:

• Omitting braces for single statement
• Misreading error as variable issue
• Confusing println with Println

5. Given this Go code, what will be the output?

sum := 0
for i := 1; i <= 5; i++ {
    if i%2 == 0 {
        continue
    }
    if sum > 5 {
        break
    }
    sum += i
}
fmt.Println(sum)

hard

A. 6

B. 9

C. 10

D. 5

Solution

1. Step 1: Trace loop with continue and break

   Loop i=1 to 5, skip even i (2,4). Add odd i to sum until sum > 5, then break.

2. Step 2: Calculate sum step-by-step

   i=1 (odd): sum=0+1=1
   i=2 (even): continue, skip
   i=3 (odd): sum=1+3=4
   i=4 (even): continue, skip
   i=5 (odd): sum=4+5=9 but before adding, sum=4 which is not >5, so add 5 sum=9. Now sum >5, break after this iteration.

3. Step 3: Check when break occurs

   Break happens after sum=9, but condition checks sum >5 before adding i=5, so sum was 4 before adding 5. Actually, break triggers only if sum >5 before adding i.

4. Step 4: Correct calculation

   At i=5, sum=4 (not >5), so add 5 sum=9. Next iteration would be i=6 (loop ends). So break never triggers because sum >5 check is before adding i.

5. Final Answer:

   9 -> Option B

6. Quick Check:

   Sum after adding odd numbers until break = 9 [OK]

Hint: Check continue and break order carefully [OK]

Common Mistakes:

• Adding after break condition incorrectly
• Ignoring continue skipping even numbers
• Misunderstanding break timing