Increment and decrement in Go - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to increment the variable count by 1.

Go

package main

import "fmt"

func main() {
    count := 5
    count[1]
    fmt.Println(count)
}

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

A++

B+=

C++=

D--

Attempts:

3 left

💡 Hint

Common Mistakes

Using '+=' causes a syntax error because it requires an operand like 1 after it.

Using '--' decreases the value instead of increasing.

In Go, count++ increases count by 1. The ++ operator is a postfix statement, not an expression.

2fill in blank

medium

Complete the code to decrement the variable num by 1 using the correct operator.

Go

package main

import "fmt"

func main() {
    num := 10
    num[1] 1
    fmt.Println(num)
}

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

A-=

B+=

C++

D--

Attempts:

3 left

💡 Hint

Common Mistakes

Using '--' with a value causes syntax error.

Using '+=' increases the value instead of decreasing.

The operator -= subtracts a value from a variable. So num -= 1 decreases num by 1.

3fill in blank

hard

Fix the error in the code to correctly increment value by 1.

Go

package main

import "fmt"

func main() {
    value := 3
    value [1]
    fmt.Println(value)
}

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

A--

B++

C++ 1

D+= 1

Attempts:

3 left

💡 Hint

Common Mistakes

Using '++' causes syntax error due to the space separating variable and operator.

Using '++ 1' is invalid syntax.

In Go, value += 1 correctly increments value by 1 given the space after value. The ++ operator requires no space: value++.

4fill in blank

hard

Fill both blanks to create a map of words to their lengths, including only words longer than 3 characters.

Go

package main

import "fmt"

func main() {
    words := []string{"go", "code", "play", "fun"}
    lengths := make(map[string]int)
    for _, word := range words {
        if len(word) > 3 {
            lengths[[1]] = len([2])
        }
    }
    fmt.Println(lengths)
}

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

A"word"

Bword

Cwords

D"words"

Attempts:

3 left

💡 Hint

Common Mistakes

Using '"word"' (quoted literal) instead of variable word for dynamic key.

Using the whole list 'words' instead of the current 'word' for length.

In the loop's if block, use word as the key (string variable, no quotes). Use word for len(word) value.

5fill in blank

hard

Fill all three blanks to create a map of uppercase words to their lengths, including only words longer than 3 characters.

Go

package main

import (
    "fmt"
    "strings"
)

func main() {
    words := []string{"go", "code", "play", "fun"}
    lengths := make(map[string]int)
    for _, word := range words {
        if len(word) [3] 3 {
            lengths[[1]] = [2]
        }
    }
    fmt.Println(lengths)
}

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

Astrings.ToUpper(word)

Blen(word)

C>

Dword

Attempts:

3 left

💡 Hint

Common Mistakes

Using the original word instead of uppercase as key.

Using '<' instead of '>' in the condition.

Use strings.ToUpper(word) to convert the word to uppercase for the key. Use len(word) for the value. The condition len(word) > 3 filters words longer than 3 characters.

Practice

1. What does the expression i++ do in Go?

easy

A. Decreases the value of i by 1

B. Increases the value of i by 1

C. Multiplies the value of i by 2

D. Divides the value of i by 2

Solution

1. Step 1: Understand the operator meaning

   The ++ operator in Go adds 1 to the variable it is used on.

2. Step 2: Apply to variable i

   Using i++ increases the value of i by exactly 1.

3. Final Answer:

   Increases the value of i by 1 -> Option B

4. Quick Check:

   i++ means add 1 [OK]

Hint: Remember ++ means add one, -- means subtract one [OK]

Common Mistakes:

• Confusing ++ with --
• Thinking ++ multiplies or divides
• Using ++ as a function

2. Which of the following is the correct syntax to decrease a variable count by 1 in Go?

easy

A. count--

B. --count

C. count++

D. count =- 1

Solution

1. Step 1: Identify decrement syntax in Go

   In Go, variable-- is the correct way to subtract 1 from a variable.

2. Step 2: Check each option

   count-- uses count--, which is correct. --count is invalid prefix decrement in Go. count++ increases count. count =- 1 is invalid syntax.

3. Final Answer:

   count-- -> Option A

4. Quick Check:

   Use -- to subtract one [OK]

Hint: Use -- to subtract one, not =- [OK]

Common Mistakes:

• Using --count instead of count--
• Confusing ++ and --
• Using count += 1 to decrement

3. What is the output of this Go code?

package main
import "fmt"
func main() {
  x := 5
  x++
  x--
  x++
  fmt.Println(x)
}

medium

A. Syntax error

B. 5

C. 7

D. 6

Solution

1. Step 1: Trace the increments and decrements

   Start with x = 5. Then x++ makes x = 6. Then x-- makes x = 5 again. Then x++ makes x = 6.

2. Step 2: Print the final value

   The final value of x is 6, so fmt.Println(x) prints 6.

3. Final Answer:

   6 -> Option D

4. Quick Check:

   5 +1 -1 +1 = 6 [OK]

Hint: Add and subtract step by step to find final value [OK]

Common Mistakes:

• Ignoring one increment or decrement
• Thinking increments happen before assignment
• Confusing output with syntax error

4. Find the error in this Go code snippet:

package main
func main() {
  var n int = 10
  n++
  n--
  n = n++
}

medium

A. Assigning n = n++ causes a compile error

B. n-- cannot be used on integers

C. Using n++ as a statement is invalid

D. Variable n must be declared without type

Solution

1. Step 1: Understand usage of n++ in Go

   In Go, n++ and n-- are statements that increment or decrement n by 1. They cannot be used as expressions.

2. Step 2: Analyze the assignment n = n++

   Assigning n = n++ tries to use n++ as a value, which is invalid in Go and causes a compile error.

3. Final Answer:

   Assigning n = n++ causes a compile error -> Option A

4. Quick Check:

   n++ is a statement, not an expression [OK]

Hint: Remember n++ can't be assigned; it's a statement only [OK]

Common Mistakes:

• Trying to assign n = n++
• Thinking n-- is invalid on int
• Ignoring Go's statement-only rule for ++/--

5. You want to count down from 3 to 1 using a for loop in Go. Which code correctly uses decrement to do this?

for i := 3; i > 0; ??? {
  fmt.Println(i)
}

hard

A. i += 1

B. i++

C. i--

D. --i

Solution

1. Step 1: Understand the loop goal

   The loop should count down from 3 to 1, so i must decrease each time.

2. Step 2: Choose the correct decrement expression

   Using i-- decreases i by 1 each loop, matching the goal. Options A, B, and C are wrong: A and B increase i, C is invalid prefix --i in Go.

3. Final Answer:

   i-- -> Option C

4. Quick Check:

   Use i-- to count down in loops [OK]

Hint: Use i-- to count down, i++ to count up [OK]

Common Mistakes:

• Using i++ when counting down
• Using i += 1 instead of i--
• Confusing decrement syntax in for loops