How Strings Work Differently Across Languages in DSA Go - Debugging & Practice

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this Go code with string indexing?

Consider the following Go code that indexes a string containing Unicode characters. What will be printed?

DSA Go

package main
import "fmt"
func main() {
    s := "Go💻"
    fmt.Printf("%d\n", s[2])
}

A 240

B 111

C SyntaxError

D RuntimeError

💡 Hint

Remember that indexing a string in Go returns a byte, not a rune.

In Go, strings are byte slices. The emoji 💻 is a multi-byte UTF-8 character. Indexing s[2] returns the third byte of the string, which is 240 in decimal.

❓ Predict Output

intermediate

What is the output of this Python string slicing code?

Given the Python code below, what is the output?

DSA Go

s = 'café'
print(s[3])

A IndexError

B SyntaxError

C e

D é

💡 Hint

Python strings are sequences of Unicode characters.

Python strings are Unicode sequences. Index 3 corresponds to the character 'é'.

🔧 Debug

advanced

Why does this JavaScript string length differ from expected?

Consider this JavaScript code snippet. Why does the length property not match the number of visible characters?

DSA Go

const s = '👩👩👧👦';
console.log(s.length);

A Because length counts Unicode code points correctly

B Because length counts UTF-16 code units, not user-perceived characters

C Because length counts bytes in UTF-8 encoding

D Because length counts grapheme clusters

💡 Hint

JavaScript strings use UTF-16 encoding internally.

JavaScript's length counts UTF-16 code units, so complex emojis made of multiple code units have length greater than 1.

🧠 Conceptual

advanced

How do Go and Python differ in string mutability?

Which statement correctly describes the difference in string mutability between Go and Python?

A Go strings are mutable; Python strings are immutable

B Both Go and Python strings are mutable

C Both Go and Python strings are immutable

D Go strings are immutable; Python strings are mutable

💡 Hint

Think about whether you can change characters inside a string directly.

Both Go and Python strings cannot be changed after creation; they are immutable.

🚀 Application

expert

How to correctly iterate over Unicode characters in Go?

Given the Go string s := "Hello, 世界", which code snippet correctly prints each Unicode character on a new line?

A for _, r := range s { fmt.Println(string(r)) }

B for i, _ := range s { fmt.Println(string(s[i])) }

C for i := 0; i < len(s); i++ { fmt.Println(string(s[i])) }

D for i := 0; i < len(s); i += 2 { fmt.Println(string(s[i])) }

💡 Hint

Use range to iterate over runes, not bytes.

Using 'for _, r := range s' iterates over runes (Unicode code points), correctly handling multi-byte characters.

Practice

1. In Go, what is the type of a string internally?
var s = "hello"

easy

A. A sequence of bytes representing UTF-8 encoded characters

B. An array of Unicode code points (runes)

C. A linked list of characters

D. A pointer to a null-terminated character array

Solution

1. Step 1: Understand Go string representation

   Go strings are immutable sequences of bytes, typically UTF-8 encoded.

2. Step 2: Compare with other languages

   Unlike some languages that use arrays of Unicode code points, Go uses bytes internally.

3. Final Answer:

   A sequence of bytes representing UTF-8 encoded characters -> Option A

4. Quick Check:

   Go strings = UTF-8 bytes [OK]

Hint: Remember Go strings are byte sequences, not rune arrays [OK]

Common Mistakes:

• Thinking Go strings store runes directly
• Assuming null-terminated strings like C
• Confusing with linked list or array types

2. Which of the following is the correct way to get the length of a string in Go?
s := "hello"

easy

A. length(s)

B. s.length()

C. len(s)

D. s.len

Solution

1. Step 1: Recall Go built-in function for length

   Go uses the built-in function len() to get the length of strings and slices.

2. Step 2: Check other options

   Methods like s.length() or s.len do not exist in Go; length(s) is not valid syntax.

3. Final Answer:

   len(s) -> Option C

4. Quick Check:

   Use len() for string length in Go [OK]

Hint: Use len() function to get string length in Go [OK]

Common Mistakes:

• Using method calls like s.length() from other languages
• Trying to access length as a property
• Using undefined functions like length()

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

package main
import "fmt"
func main() {
  s := "Go😊"
  fmt.Println(len(s))
}

medium

A. 3

B. 6

C. 4

D. 5

Solution

1. Step 1: Analyze string content and encoding

   The string "Go😊" has 'G' and 'o' as 1 byte each, and the emoji '😊' is a 4-byte UTF-8 character.

2. Step 2: Calculate total byte length

   Total bytes = 1 (G) + 1 (o) + 4 (😊) = 6 bytes.

3. Step 3: Check len() output

   len(s) returns the number of bytes, so output is 6.

4. Final Answer:

   6 -> Option B

5. Quick Check:

   len() counts bytes, not characters [OK]

Hint: len() returns bytes count, not character count [OK]

Common Mistakes:

• Assuming len() returns number of characters
• Ignoring multi-byte UTF-8 characters
• Confusing bytes with runes

4. Identify the error in this Go code that tries to print each character of a string:

package main
import "fmt"
func main() {
  s := "Go"
  for i := 0; i < len(s); i++ {
    fmt.Println(s[i])
  }
}

medium

A. It prints byte values, not characters

B. Syntax error in for loop

C. s[i] is invalid syntax

D. Missing import for fmt

Solution

1. Step 1: Understand s[i] in Go strings

   Accessing s[i] returns the byte at index i, not a character or string.

2. Step 2: Check output of fmt.Println(s[i])

   It prints the numeric byte value (ASCII code), not the character itself.

3. Final Answer:

   It prints byte values, not characters -> Option A

4. Quick Check:

   s[i] = byte, prints number [OK]

Hint: s[i] gives byte, convert to rune or string to print char [OK]

Common Mistakes:

• Expecting s[i] to print characters directly
• Ignoring byte vs rune difference
• Assuming syntax error where none exists

5. How can you correctly iterate over each Unicode character in a Go string to print them?
Choose the correct code snippet.

hard

A. for i := 0; i < len(s); i++ { fmt.Println(string(s[i])) }

B. for i := range s { fmt.Println(s[i]) }

C. for i, c := range s { fmt.Println(s[i]) }

D. for _, r := range s { fmt.Println(string(r)) }

Solution

1. Step 1: Understand iteration over strings in Go

   Using 'for _, r := range s' iterates over runes (Unicode code points), not bytes.

2. Step 2: Check printing each character

   Converting rune 'r' to string prints the actual character correctly.

3. Step 3: Analyze other options

   for i := 0; i < len(s); i++ { fmt.Println(string(s[i])) } prints bytes as strings, which may break multi-byte chars; C and D print bytes, not runes.

4. Final Answer:

   for _, r := range s { fmt.Println(string(r)) } -> Option D

5. Quick Check:

   Use range to get runes for correct Unicode iteration [OK]

Hint: Use 'for _, r := range s' to iterate Unicode chars [OK]

Common Mistakes:

• Iterating by byte index instead of runes
• Printing bytes as characters causing errors
• Confusing index and rune variables