Regex Substitution - HackerRank Solution Python

Regex Substitution - HackerRank is a problem from HackerRank in the domain Python subdomain Regex called Regex Substitution. It’s one of the medium level problems of Python. We have to solve this problem in python.

Problem Statement and Explanation

In this problem, we have to use regular expression to substitute all && and || symbols with and and or respectively using re.sub() method.

Input Format

• The first line contains the integer, N. The next N lines each contain a line of the text.
• The next N lines contains the HTML code.

Output Format

Print the modified HTML code for each test case as a single line and the modified HTML code should be printed as it was received as input.

Regex Substitution Solution in Python

Explanation of Solution

• The first line imports the re module, which provides regular expression functionality in Python.

• The substitute_text_in_string() function takes a string as input and returns a new string with the && and || characters replaced with and and or, respectively.

• The function works by first creating a regular expression pattern that matches the && and || characters, followed by two spaces.

• The re.sub() function is then used to substitute the pattern with the replacement text, which is either and or or.

• The lambda expression is used to determine the replacement text, depending on the value of the matched group.

• The if name == ‘ main ’: block is used to execute the function when the code is run as a script.

• The first -line in the block prompts the user to enter the number of lines of text.

• The next line creates an empty string to store the input text.

• The following loop iterates through the number of lines and appends each line to the text string.

• The last line calls the substitute_text_in_string() function to replace the && and || characters in the text string.

Complexity of the Solution

Time complexity

The time complexity of the solution is O(n), where n is the number of lines of text. This is because the substitute_text_in_string() function is called n times, once for each line of text.

The re.sub() function takes O(m) time, where m is the length of the regular expression pattern.

In this case, the regular expression pattern is of length 8, so the re.sub() function takes O(8) time. Therefore, the overall time complexity of the solution is O(n + 8) = O(n).

Space complexity

The space complexity of the solution is O(n), where n is the number of lines of text.

This is because the substitute_text_in_string() function creates a new string with the && and || characters replaced. The new string is of length n, so the space complexity of the solution is O(n).

In conclusion, the time and space complexity of the solution are both O(n).

Problem statement is taken from Hackerrank, and the solutions are implemented by CodePerfectPlus team