Why Sorting Matters and How It Unlocks Other Algorithms in DSA Go - Test Your Knowledge

Practice - 5 Tasks

1fill in blank

easy

Complete the code to sort the slice of integers in ascending order.

DSA Go

package main

import (
	"fmt"
	"sort"
)

func main() {
	numbers := []int{5, 3, 8, 1, 2}
	sort.[1](numbers)
	fmt.Println(numbers)
}

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

AInts

BSortStrings

CSortFloat64s

DSort

Attempts:

3 left

💡 Hint

Common Mistakes

Using SortStrings instead of Ints causes a type error.

Using SortFloat64s on integer slices is incorrect.

The sort.Ints function sorts a slice of integers in ascending order.

2fill in blank

medium

Complete the code to check if the slice is sorted in ascending order.

DSA Go

package main

import (
	"fmt"
	"sort"
)

func main() {
	numbers := []int{1, 2, 3, 4, 5}
	isSorted := sort.[1](sort.IntSlice(numbers))
	fmt.Println(isSorted)
}

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AIsSortedInts

BSorted

CIsSorted

DCheckSorted

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'Sorted' instead of 'IsSorted' causes a compile error.

There is no function named 'IsSortedInts' in the sort package.

The sort.IsSorted function returns true if the slice is sorted in ascending order.

3fill in blank

hard

Fix the error in the code to sort a slice of strings alphabetically.

DSA Go

package main

import (
	"fmt"
	"sort"
)

func main() {
	words := []string{"banana", "apple", "cherry"}
	sort.[1](words)
	fmt.Println(words)
}

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

ASortInts

BSortFloat64s

CSort

DStrings

Attempts:

3 left

💡 Hint

Common Mistakes

Using SortInts on strings causes a type error.

Using SortFloat64s on strings is invalid.

The sort.Strings function sorts a slice of strings alphabetically.

4fill in blank

hard

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

DSA Go

package main

import "fmt"

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

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A>

Blen(word)

C<

Dword

Attempts:

3 left

💡 Hint

Common Mistakes

Using '<' instead of '>' causes wrong filtering.

Using 'word' as map value instead of length.

The condition len(word) > 3 filters words longer than 3 characters, and len(word) gives the length value for the map.

5fill in blank

hard

Fill all three blanks to create a map of uppercase words to their lengths for words longer than 2 characters.

DSA Go

package main

import (
	"fmt"
	"strings"
)

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

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

A>

Blen(word)

CToUpper

DToLower

Attempts:

3 left

💡 Hint

Common Mistakes

Using '<' instead of '>' causes wrong filtering.

Using ToLower instead of ToUpper changes case incorrectly.

Using 'word' instead of 'len(word)' as map value.

The condition len(word) > 2 filters words longer than 2 characters. strings.ToUpper(word) converts words to uppercase keys, and len(word) is the map value.

Practice

1. Why is sorting an important step before applying many algorithms in data processing?

easy

A. It encrypts data for security

B. It removes duplicate data automatically

C. It compresses the data to save space

D. It organizes data to make searching and comparisons faster

Solution

1. Step 1: Understand sorting's role in data organization

   Sorting arranges data in a specific order, making it easier to find or compare elements quickly.

2. Step 2: Connect sorting to algorithm efficiency

   Many algorithms like binary search or merge operations rely on sorted data to work efficiently.

3. Final Answer:

   It organizes data to make searching and comparisons faster -> Option D

4. Quick Check:

   Sorting improves search speed = A [OK]

Hint: Sorting arranges data to speed up searching and comparisons [OK]

Common Mistakes:

• Thinking sorting removes duplicates
• Confusing sorting with compression
• Assuming sorting encrypts data

2. Which of the following is the correct way to sort an integer slice named nums in Go using the standard library?

easy

A. sort.Ints(nums)

B. nums.sort()

C. sort(nums)

D. nums.SortInts()

Solution

1. Step 1: Recall Go's sorting syntax

   Go's standard library provides the sort package with the function Ints(slice []int) to sort integer slices.

2. Step 2: Match the correct function call

   The correct call is sort.Ints(nums), which sorts the slice in place.

3. Final Answer:

   sort.Ints(nums) -> Option A

4. Quick Check:

   Use sort.Ints(slice) to sort int slices in Go [OK]

Hint: Use sort.Ints(slice) to sort integer slices in Go [OK]

Common Mistakes:

• Trying to call sort as a method on the slice
• Using incorrect function names like sort()
• Assuming slice has a SortInts method

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

package main
import (
  "fmt"
  "sort"
)
func main() {
  nums := []int{5, 3, 8, 1}
  sort.Ints(nums)
  fmt.Println(nums)
}

medium

A. [1 3 5 8]

B. [5 3 8 1]

C. [8 5 3 1]

D. [1 5 3 8]

Solution

1. Step 1: Understand the initial slice

   The slice nums starts as [5, 3, 8, 1].

2. Step 2: Apply sort.Ints to nums

   sort.Ints sorts the slice in ascending order, changing nums to [1, 3, 5, 8].

3. Final Answer:

   [1 3 5 8] -> Option A

4. Quick Check:

   Sorting [5 3 8 1] gives [1 3 5 8] [OK]

Hint: sort.Ints sorts slice ascending; print shows sorted slice [OK]

Common Mistakes:

• Expecting original order after sorting
• Confusing descending with ascending order
• Misreading slice print format

4. The following Go code tries to sort a slice of strings but causes a compile error. What is the error and how to fix it?

package main
import (
  "fmt"
)
func main() {
  words := []string{"pear", "apple", "orange"}
  words.Sort()
  fmt.Println(words)
}

medium

A. Error: cannot print slice; fix by converting to string

B. Error: missing import fmt; fix by adding import fmt

C. Error: words.Sort() undefined; fix by using sort.Strings(words)

D. No error; code runs correctly

Solution

1. Step 1: Identify the cause of the error

   The slice words does not have a Sort() method; this causes a compile error.

2. Step 2: Apply the correct sorting function

   Use sort.Strings(words) from the sort package to sort string slices.

3. Final Answer:

   Error: words.Sort() undefined; fix by using sort.Strings(words) -> Option C

4. Quick Check:

   Use sort.Strings(slice) to sort string slices [OK]

Hint: Use sort.Strings(slice) to sort strings, not slice.Sort() [OK]

Common Mistakes:

• Calling Sort() method on slice directly
• Forgetting to import sort package
• Assuming fmt.Println can't print slices

5. You have two sorted slices of integers, a := []int{1, 4, 7} and b := []int{2, 5, 6}. Which approach best merges them into a single sorted slice efficiently?

hard

A. Concatenate slices and then sort the combined slice

B. Use two pointers to merge both slices in one pass

C. Append b to a and remove duplicates

D. Sort each slice separately again

Solution

1. Step 1: Understand the problem of merging sorted slices

   Both slices are already sorted, so merging can be done efficiently without full sorting.

2. Step 2: Use two-pointer technique for efficient merge

   Use two pointers, one for each slice, to pick the smaller element step-by-step, creating a merged sorted slice in one pass.

3. Final Answer:

   Use two pointers to merge both slices in one pass -> Option B

4. Quick Check:

   Two-pointer merge is efficient for sorted slices [OK]

Hint: Merge sorted slices with two pointers for O(n) efficiency [OK]

Common Mistakes:

• Sorting concatenated slices wastes time
• Removing duplicates is unnecessary here
• Sorting slices again is redundant