Labelled break and continue in Go - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of labelled break in nested loops

What is the output of this Go program using a labelled break?

Go

package main
import "fmt"
func main() {
OuterLoop:
for i := 1; i <= 3; i++ {
    for j := 1; j <= 3; j++ {
        if i*j > 3 {
            break OuterLoop
        }
        fmt.Printf("%d,%d ", i, j)
    }
}
}

A 1,1 1,2 2,1

B 1,1 1,2 1,3 2,1

C 1,1 1,2 2,1 2,2

D 1,1 1,2 1,3 2,1 2,2

💡 Hint

Remember that labelled break exits the outer loop immediately.

The inner loop prints pairs until i*j > 3. When i=2 and j=2, 2*2=4 > 3, so break OuterLoop stops all loops. So output stops after printing 1,1 1,2 1,3 2,1.

❓ Predict Output

intermediate

Output of labelled continue in nested loops

What is the output of this Go program using a labelled continue?

Go

package main
import "fmt"
func main() {
Outer:
for i := 1; i <= 3; i++ {
    for j := 1; j <= 3; j++ {
        if i == j {
            continue Outer
        }
        fmt.Printf("%d,%d ", i, j)
    }
}
}

A 2,1 3,1 3,2

B 1,2 1,3 2,1 2,3 3,1

C 1,2 1,3 2,1 2,3 3,1 3,2 3,3

D 1,2 1,3 2,1 2,3 3,1 3,2

💡 Hint

Labelled continue skips to the next iteration of the outer loop, skipping remaining inner loop iterations.

When i == j, continue Outer skips remaining inner loop iterations and proceeds to the next outer loop iteration (i++). For i=1: skips at j=1 (no output). i=2: prints 2,1, skips at j=2. i=3: prints 3,1 3,2, skips at j=3. Output: 2,1 3,1 3,2

🔧 Debug

advanced

Identify the error with labelled break usage

What error does this Go code produce?

Go

package main
func main() {
    for i := 0; i < 3; i++ {
        if i == 1 {
            break Outer
        }
    }
}

A no error, program runs fine

B runtime panic: label not found

C compile error: undefined label Outer

D compile error: break statement not in loop or switch

💡 Hint

Labels must be declared before use.

The label Outer is not declared anywhere, so the compiler reports undefined label error.

❓ Predict Output

advanced

Effect of labelled continue on outer loop variable

What is the output of this Go program?

Go

package main
import "fmt"
func main() {
Outer:
for i := 1; i <= 2; i++ {
    for j := 1; j <= 3; j++ {
        if j == 2 {
            continue Outer
        }
        fmt.Printf("%d,%d ", i, j)
    }
}
}

A 1,1 2,1 2,3

B 1,1 2,1 2,2 2,3

C 1,1 1,3 2,1 2,3

D 1,1 2,1

💡 Hint

Labelled continue skips to next iteration of outer loop immediately.

When j == 2, continue Outer skips the rest of inner loop and increments i. So only j=1 prints for each i.

🧠 Conceptual

expert

Understanding labelled break and continue behavior

Which statement about labelled break and continue in Go is TRUE?

A Labelled break exits the loop with the matching label; labelled continue skips to the next iteration of the labelled loop.

B Labelled break and continue can only be used with for loops, not switch statements.

C Labelled break skips the current iteration of the labelled loop; labelled continue exits the labelled loop entirely.

D Labelled continue can be used without a label to skip the current iteration of the innermost loop.

💡 Hint

Think about what break and continue do normally and how labels change their target.

Labelled break exits the loop with the label; labelled continue skips to the next iteration of that labelled loop. They can be used with for and switch. Unlabelled continue skips current iteration of innermost loop.

Practice

1. What is the main purpose of using a labelled break in Go nested loops?

easy

A. To declare a new variable inside the loop

B. To exit from an outer loop directly

C. To restart the entire program

D. To skip the current iteration of the inner loop

Solution

1. Step 1: Understand labelled break usage

   A labelled break lets you exit a specific loop, usually an outer one, directly from inside nested loops.

2. Step 2: Compare with normal break

   Normal break exits only the innermost loop, but labelled break can exit outer loops by specifying the label.

3. Final Answer:

   To exit from an outer loop directly -> Option B

4. Quick Check:

   Labelled break = exit outer loop [OK]

Hint: Labelled break jumps out of outer loops directly [OK]

Common Mistakes:

• Thinking break skips iteration instead of exiting loop
• Confusing labelled break with continue
• Assuming break restarts loops

2. Which of the following is the correct syntax to use a labelled continue in Go?

easy

A. continue labelName

B. continue to labelName

C. continue(labelName)

D. continue; labelName

Solution

1. Step 1: Recall labelled continue syntax

   In Go, to continue a labelled loop, you write continue labelName without parentheses or extra keywords.

2. Step 2: Check other options

   Options A, B, and D use incorrect syntax like extra words, parentheses, or semicolons which are invalid in Go.

3. Final Answer:

   continue labelName -> Option A

4. Quick Check:

   Labelled continue syntax = continue labelName [OK]

Hint: Use 'continue' followed by label name without punctuation [OK]

Common Mistakes:

• Adding parentheses around label
• Using extra words like 'to' or semicolons
• Confusing break and continue syntax

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

outer:
for i := 1; i <= 3; i++ {
    for j := 1; j <= 3; j++ {
        if i*j > 3 {
            break outer
        }
        fmt.Print(i*j, " ")
    }
}

medium

A. 1 2 3 2

B. 1 2 3 2 4 6 3 6 9

C. 1 2 2 3

D. 1 2 2 3 3

Solution

1. Step 1: Trace the nested loops and condition

   For i=1, j=1 to 3: i*j = 1,2,3 (all ≤ 3), so prints "1 2 3 ". For i=2, j=1: i*j=2 (≤3), prints "2 ". Next j=2: i*j=4 (>3), triggers break outer which exits the outer loop immediately.

2. Step 2: Understand break outer effect

   Since break outer exits both loops, no further printing occurs after i=2, j=2 check.

3. Final Answer:

   1 2 3 2 -> Option A

4. Quick Check:

   Labelled break exits outer loop at i*j>3 [OK]

Hint: Labelled break exits all loops at condition [OK]

Common Mistakes:

• Ignoring labelled break effect and continuing loops
• Confusing break with continue
• Miscomputing i*j values

4. Identify the error in this Go code snippet using labelled continue:

outer:
for i := 0; i < 3; i++ {
    for j := 0; j < 3; j++ {
        if i == j {
            continue
        }
        fmt.Println(i, j)
    }
}

medium

A. continue cannot be used inside nested loops

B. Label 'outer' is not defined before the loops

C. Missing label after continue to specify which loop to continue

D. fmt.Println syntax is incorrect

Solution

1. Step 1: Check labelled continue usage

   The code defines label 'outer' but uses plain continue inside inner loop. To continue the outer loop, it must be continue outer.

2. Step 2: Understand effect of missing label

   Without label, continue only skips current inner loop iteration, not the outer loop. The label is unused, which is likely a mistake.

3. Final Answer:

   Missing label after continue to specify which loop to continue -> Option C

4. Quick Check:

   Labelled continue needs label after continue [OK]

Hint: Use label after continue to affect outer loops [OK]

Common Mistakes:

• Using continue without label when label is defined
• Assuming continue skips outer loop without label
• Confusing label placement

5. Given nested loops labelled outer and inner, how would you skip the rest of the current iteration of the outer loop from inside the inner loop in Go?

hard

A. Use break inner inside the inner loop

B. Use break outer inside the outer loop

C. Use continue inner inside the outer loop

D. Use continue outer inside the inner loop

Solution

1. Step 1: Understand labelled continue behavior

   Using continue outer inside the inner loop skips the rest of the current iteration of the outer loop and moves to the next iteration of the outer loop.

2. Step 2: Differentiate from break and other options

   break inner exits the inner loop, but does not skip outer loop iteration. continue inner affects inner loop only. break outer exits the outer loop entirely.

3. Final Answer:

   Use continue outer inside the inner loop -> Option D

4. Quick Check:

   Labelled continue skips outer loop iteration [OK]

Hint: Use 'continue' with outer label to skip outer iteration [OK]

Common Mistakes:

• Using break instead of continue to skip iteration
• Applying continue to wrong loop label
• Confusing break and continue effects