String replacement in MATLAB - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this string replacement code?

Consider the following MATLAB code that replaces a substring in a string. What will be the output?

MATLAB

str = 'I love apples';
newStr = strrep(str, 'apples', 'oranges');
disp(newStr);

A I love oranges

B I love apples

C I love applesoranges

D I love

💡 Hint

The function strrep replaces all occurrences of the old substring with the new substring.

The strrep function replaces 'apples' with 'oranges' in the original string, so the output is 'I love oranges'.

❓ Predict Output

intermediate

What does this code output after replacing multiple substrings?

This MATLAB code replaces multiple substrings sequentially. What is the final output?

MATLAB

str = 'cat bat rat';
str = strrep(str, 'bat', 'dog');
str = strrep(str, 'rat', 'fox');
disp(str);

A cat dog fox

B cat dog rat

C cat bat rat

D dog cat fox

💡 Hint

Each strrep call replaces all occurrences of the target substring.

First 'bat' is replaced by 'dog', then 'rat' is replaced by 'fox', resulting in 'cat dog fox'.

❓ Predict Output

advanced

What is the output of this code using regexprep for string replacement?

This MATLAB code uses regexprep to replace all digits with '#'. What is the output?

MATLAB

str = 'Room 123, Floor 4';
newStr = regexprep(str, '\\d', '#');
disp(newStr);

A Room #23, Floor 4

B Room 123, Floor 4

C Room ###, Floor #

D Room ###, Floor 4

💡 Hint

The pattern '\d' matches each digit individually.

regexprep replaces each digit with '#', so '123' becomes '###' and '4' becomes '#'.

❓ Predict Output

advanced

What error does this code produce when using strrep incorrectly?

What error will this MATLAB code produce?

MATLAB

str = 'hello world';
newStr = strrep(str, 'world');
disp(newStr);

A hello

B Error: Not enough input arguments.

C hello world

D Error: Undefined function or variable 'strrep'.

💡 Hint

Check the number of arguments strrep requires.

strrep requires three arguments: the original string, the substring to replace, and the replacement substring. Missing the third argument causes an error.

🧠 Conceptual

expert

How many replacements occur in this code using strrep with overlapping substrings?

Given the code below, how many replacements does strrep perform?

MATLAB

str = 'aaaa';
newStr = strrep(str, 'aa', 'b');
disp(newStr);

A 1

B 4

C 3

D 2

💡 Hint

strrep does not replace overlapping occurrences twice.

strrep replaces non-overlapping occurrences from left to right. 'aaaa' has two non-overlapping 'aa' substrings: positions 1-2 and 3-4, so 2 replacements occur.