String comparison in MATLAB - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of strcmp with different cases

What is the output of this MATLAB code snippet?

MATLAB

result = strcmp('Hello', 'hello');
disp(result);

A Error: Undefined function or variable 'strcmp'.

B 1

C 0

D 2

💡 Hint

strcmp is case-sensitive and returns 1 if strings match exactly.

strcmp compares two strings exactly, including case. 'Hello' and 'hello' differ in case, so strcmp returns 0.

❓ Predict Output

intermediate

Using strcmpi for case-insensitive comparison

What will this MATLAB code display?

MATLAB

result = strcmpi('MATLAB', 'matlab');
disp(result);

A 1

B Error: Undefined function or variable 'strcmpi'.

C 0

D NaN

💡 Hint

strcmpi compares strings ignoring case differences.

strcmpi returns 1 because it ignores case and the strings match.

❓ Predict Output

advanced

Comparing string arrays with strcmp

What is the output of this code?

MATLAB

A = {'cat', 'dog', 'bird'};
B = {'cat', 'Dog', 'bird'};
result = strcmp(A, B);
disp(result);

A [1 0 1]

B [1 1 1]

C [0 0 0]

D Error: Cell contents reference from a non-cell array object.

💡 Hint

strcmp compares each pair of strings element-wise and is case-sensitive.

The second elements differ in case ('dog' vs 'Dog'), so strcmp returns 0 for that element.

❓ Predict Output

advanced

Behavior of isequal with strings

What does this MATLAB code print?

MATLAB

str1 = 'Test';
str2 = 'test';
result = isequal(str1, str2);
disp(result);

A 1

B 0

C Error: Undefined function or variable 'isequal'.

D NaN

💡 Hint

isequal compares values exactly, including case.

isequal returns 0 because 'Test' and 'test' differ in case.

🧠 Conceptual

expert

Understanding strcmp return values

Which option correctly describes the return value of strcmp when comparing two strings in MATLAB?

A It returns a string 'true' or 'false' depending on the comparison.

B It returns the number of matching characters at the start of the strings.

C It returns the ASCII difference between the first non-matching characters.

D It returns a logical 1 if the strings are exactly the same, otherwise logical 0.

💡 Hint

Think about what strcmp returns when strings match exactly.

strcmp returns logical 1 (true) if strings match exactly, else logical 0 (false). It does not return counts or ASCII differences.

Practice

1. Which MATLAB function is used to compare two strings with case sensitivity?

easy

A. strcmpi

B. strcmp

C. strcomp

D. strcompare

Solution

1. Step 1: Understand string comparison functions

   MATLAB provides strcmp for case-sensitive string comparison and strcmpi for case-insensitive comparison.

2. Step 2: Identify the correct function for case-sensitive comparison

   strcmp compares strings exactly, including letter case, so it is the correct choice.

3. Final Answer:

   strcmp -> Option B

4. Quick Check:

   Case-sensitive comparison = strcmp [OK]

Hint: Use strcmp for exact case-sensitive string checks [OK]

Common Mistakes:

• Confusing strcmp with strcmpi
• Using non-existent functions like strcomp
• Assuming strcmpi is case-sensitive

2. Which of the following is the correct syntax to compare two strings s1 and s2 ignoring case in MATLAB?

easy

A. strcmpi(s1 == s2)

B. strcmp(s1, s2)

C. strcmpi(s1, s2)

D. strcmp(s1 == s2)

Solution

1. Step 1: Recall syntax for case-insensitive comparison

   strcmpi compares two strings ignoring case and takes two string inputs as separate arguments.

2. Step 2: Identify correct syntax

   strcmpi(s1, s2) uses strcmpi with two string arguments correctly. Options C and D incorrectly use '==' inside the function, which is invalid.

3. Final Answer:

   strcmpi(s1, s2) -> Option C

4. Quick Check:

   Case-insensitive syntax = strcmpi(s1, s2) [OK]

Hint: Use strcmpi(s1, s2) for ignoring case in string comparison [OK]

Common Mistakes:

• Using '==' inside strcmp or strcmpi
• Mixing up strcmp and strcmpi
• Passing strings as one argument with '=='

3. What is the output of the following MATLAB code?

s1 = "Hello";
s2 = "hello";
result = strcmp(s1, s2);
disp(result);

medium

A. "true"

B. 1

C. Error

D. 0

Solution

1. Step 1: Understand strcmp behavior

   strcmp compares strings with case sensitivity. "Hello" and "hello" differ in case.

2. Step 2: Evaluate strcmp result

   Since the strings differ in case, strcmp returns logical 0 (false), which disp prints as 0.

3. Final Answer:

   0 -> Option D

4. Quick Check:

   Case-sensitive mismatch = 0 [OK]

Hint: strcmp returns 0 if cases differ exactly [OK]

Common Mistakes:

• Assuming strcmp ignores case
• Expecting output '1' for different case
• Confusing output with string 'true'

4. Identify the error in this MATLAB code snippet for case-insensitive string comparison:

s1 = "Test";
s2 = "test";
if strcmpi(s1 == s2)
    disp('Match');
end

medium

A. Using '==' inside strcmpi causes an error

B. Missing semicolon after disp statement

C. strcmpi cannot compare strings

D. Strings must be converted to char arrays first

Solution

1. Step 1: Analyze the use of '==' inside strcmpi

   The expression s1 == s2 compares strings element-wise, returning a logical array, not a string.

2. Step 2: Understand strcmpi input requirements

   strcmpi expects two string inputs, not a logical array. Using '==' inside causes a syntax or runtime error.

3. Final Answer:

   Using '==' inside strcmpi causes an error -> Option A

4. Quick Check:

   strcmpi needs strings, not logical arrays [OK]

Hint: Do not use '==' inside strcmpi; pass strings directly [OK]

Common Mistakes:

• Using '==' inside strcmpi
• Thinking strcmpi compares logical arrays
• Ignoring input type requirements

5. You want to compare two cell arrays of strings C1 = {'Apple', 'Banana', 'Cherry'} and C2 = {'apple', 'banana', 'cherry'} ignoring case. Which MATLAB code correctly returns a logical array indicating matches?

hard

A. cellfun(@strcmpi, C1, C2)

B. strcmpi(C1{:}, C2{:})

C. cellfun(@strcmp, C1, C2)

D. strcmp(C1, C2)

Solution

1. Step 1: Understand cell array string comparison

   To compare each pair of strings in cell arrays element-wise, use cellfun with a comparison function.

2. Step 2: Choose case-insensitive comparison

   strcmpi ignores case, so cellfun(@strcmpi, C1, C2) applies it element-wise correctly.

3. Step 3: Why other options fail

   cellfun(@strcmp, C1, C2) uses case-sensitive strcmp. strcmpi(C1{:}, C2{:}) unpacks cells into multiple arguments, causing a "too many input arguments" error. strcmp(C1, C2) is case-sensitive.

4. Final Answer:

   cellfun(@strcmpi, C1, C2) -> Option A

5. Quick Check:

   Use cellfun with strcmpi for cell array case-insensitive comparison [OK]

Hint: Use cellfun(@strcmpi, C1, C2) for cell array case-insensitive compare [OK]

Common Mistakes:

• Using strcmp instead of strcmpi for ignoring case
• Unpacking cell arrays with strcmpi(C1{:}, C2{:})
• Not using cellfun for element-wise comparison