How Strings Work Differently Across Languages in DSA C++ - Code Step by Step

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a C++ string variable named 'name'.

DSA C++

std::[1] name = "Alice";

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

Afloat

Bchar

Cint

Dstring

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'char' instead of 'string' for text variables.

Forgetting to include header.

In C++, std::string is used to declare string variables.

2fill in blank

medium

Complete the code to get the length of a C++ string 'text'.

DSA C++

int length = text.[1]();

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

Alength

Bsize

Ccount

Dlen

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'len()' which is a Python method.

Using 'count()' which counts occurrences of a character.

The length() method returns the number of characters in a C++ string.

3fill in blank

hard

Fix the error in the code to concatenate two C++ strings 'a' and 'b'.

DSA C++

std::string result = a [1] b;

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

A++

B+

C&

D*

Attempts:

3 left

💡 Hint

Common Mistakes

Using '++' which is increment operator.

Using '&' which is address-of operator.

In C++, the '+' operator concatenates two strings.

4fill in blank

hard

Fill both blanks to create a C++ string from a C-style string 'charArray'.

DSA C++

std::string str([1]); // convert from [2]

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

AcharArray

BintArray

Cchar array

Dint array

Attempts:

3 left

💡 Hint

Common Mistakes

Passing an integer array instead of a char array.

Confusing variable name with type description.

To create a std::string from a C-style string, pass the char array variable.

5fill in blank

hard

Fill all three blanks to check if a C++ string 's' is empty.

DSA C++

if (s.[1]() [2] 0) {
    std::cout << "String is [3]" << std::endl;
}

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

Aempty

Blength

C==

Dnot empty

Attempts:

3 left

💡 Hint

Common Mistakes

Using empty() method incorrectly in condition.

Using wrong comparison operator.

Use length() to get string size and compare with == zero. If true, print "String is empty".

Practice

1. In C++, which of the following correctly describes how strings are stored compared to Python strings?

easy

A. C++ strings are mutable sequences of characters, while Python strings are immutable.

B. Both C++ and Python strings are immutable sequences of characters.

C. C++ strings are immutable, but Python strings are mutable.

D. Both C++ and Python strings are mutable sequences of characters.

Solution

1. Step 1: Understand C++ string mutability

   C++ std::string allows modification of characters after creation, so it is mutable.

2. Step 2: Understand Python string mutability

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

3. Final Answer:

   C++ strings are mutable sequences of characters, while Python strings are immutable. -> Option A

4. Quick Check:

   Mutability difference = C++ strings are mutable sequences of characters, while Python strings are immutable. [OK]

Hint: Remember: C++ strings can change, Python strings cannot [OK]

Common Mistakes:

• Thinking Python strings are mutable like lists
• Assuming C++ strings are immutable like Python
• Confusing character arrays with std::string
• Believing both languages treat strings the same

2. Which of the following is the correct way to declare and initialize a string in C++?

easy

A. string s = 'hello';

B. std::string s = "hello";

C. char s = "hello";

D. string s = "hello";

Solution

1. Step 1: Check correct string type and syntax

   In C++, std::string is the standard string class and strings use double quotes for literals.

2. Step 2: Validate each option

   string s = 'hello'; uses single quotes which are for single characters, char s = "hello"; uses char for multiple characters, string s = "hello"; misses std:: namespace.

3. Final Answer:

   std::string s = "hello"; -> Option B

4. Quick Check:

   C++ string declaration = std::string s = "hello"; [OK]

Hint: Use std::string and double quotes for strings in C++ [OK]

Common Mistakes:

• Using single quotes for strings
• Forgetting std:: namespace
• Using char type for strings
• Mixing C-style strings with std::string syntax

3. What will be the output of the following C++ code?

std::string s = "abc";
s[1] = 'z';
std::cout << s << std::endl;

medium

A. abc

B. Compilation error

C. abcz

D. azc

Solution

1. Step 1: Understand string indexing and mutability in C++

   std::string allows modifying characters by index, so s[1] = 'z' changes second character.

2. Step 2: Apply the change and print

   Original string "abc" changes to "azc" after s[1] = 'z'. Output is "azc".

3. Final Answer:

   azc -> Option D

4. Quick Check:

   Mutable string index change = azc [OK]

Hint: C++ strings can be changed by index directly [OK]

Common Mistakes:

• Expecting original string unchanged
• Thinking strings are immutable like Python
• Assuming compilation error due to indexing
• Confusing with C-style char arrays

4. Identify the error in the following C++ code snippet:

std::string s = "hello";
s[5] = '!';
std::cout << s << std::endl;

medium

A. Compilation error: invalid assignment

B. No error, output: hello!

C. Runtime error: out of range access

D. Output: hello

Solution

1. Step 1: Check string length and index used

   String "hello" has length 5, valid indices 0 to 4. Index 5 is out of range.

2. Step 2: Understand behavior of out-of-range index assignment

   Accessing s[5] is undefined behavior; usually causes runtime error or silent bug.

3. Final Answer:

   Runtime error: out of range access -> Option C

4. Quick Check:

   Out of bounds index causes runtime error [OK]

Hint: Check string length before indexing to avoid runtime errors [OK]

Common Mistakes:

• Assuming s[5] appends character
• Expecting compilation error instead of runtime
• Ignoring zero-based indexing
• Confusing with push_back method

5. Given the following C++ code, what will be the output?

std::string s = "test";
char* p = &s[0];
p[2] = 'x';
std::cout << s << std::endl;

How does this behavior compare to Python strings?

hard

A. Output: text; C++ strings are mutable, Python strings are immutable.

B. Output: test; Both C++ and Python strings are immutable.

C. Output: text; Both C++ and Python strings are mutable.

D. Compilation error due to pointer usage.

Solution

1. Step 1: Analyze pointer modification on std::string

   Pointer p points to first character of s. Changing p[2] modifies s[2] to 'x'.

2. Step 2: Compare with Python string behavior

   C++ strings allow character modification; Python strings do not allow such changes (immutable).

3. Final Answer:

   Output: text; C++ strings are mutable, Python strings are immutable. -> Option A

4. Quick Check:

   Pointer modifies string in C++, Python strings immutable [OK]

Hint: C++ strings allow pointer edits; Python strings never do [OK]

Common Mistakes:

• Expecting compilation error from pointer usage
• Assuming Python strings can be changed similarly
• Confusing pointer with string copy
• Ignoring zero-based indexing in modification