Introduction

In this blog post, we will explore how to solve the LeetCode problem "722" using AI. LeetCode is a popular platform for preparing for coding interviews, and with the help of AI tools like Chatmagic, we can generate solutions quickly and efficiently - helping you pass the interviews and get the job offer without having to study for months.

Problem Statement

Given a C++ program, remove comments from it. The program source is an array of strings source where source[i] is the ith line of the source code. This represents the result of splitting the original source code string by the newline character '\n'. In C++, there are two types of comments, line comments, and block comments. The string "//" denotes a line comment, which represents that it and the rest of the characters to the right of it in the same line should be ignored. The string "/" denotes a block comment, which represents that all characters until the next (non-overlapping) occurrence of "/" should be ignored. (Here, occurrences happen in reading order: line by line from left to right.) To be clear, the string "//" does not yet end the block comment, as the ending would be overlapping the beginning. The first effective comment takes precedence over others. For example, if the string "//" occurs in a block comment, it is ignored. Similarly, if the string "/" occurs in a line or block comment, it is also ignored. If a certain line of code is empty after removing comments, you must not output that line: each string in the answer list will be non-empty. There will be no control characters, single quote, or double quote characters. For example, source = "string s = "/ Not a comment. /";" will not be a test case. Also, nothing else such as defines or macros will interfere with the comments. It is guaranteed that every open block comment will eventually be closed, so "/" outside of a line or block comment always starts a new comment. Finally, implicit newline characters can be deleted by block comments. Please see the examples below for details. After removing the comments from the source code, return the source code in the same format. Example 1: Input: source = ["/Test program /", "int main()", "{ ", " // variable declaration ", "int a, b, c;", "/ This is a test", " multiline ", " comment for ", " testing /", "a = b + c;", "}"] Output: ["int main()","{ "," ","int a, b, c;","a = b + c;","}"] Explanation: The line by line code is visualized as below: /Test program / int main() { // variable declaration int a, b, c; / This is a test multiline comment for testing / a = b + c; } The string / denotes a block comment, including line 1 and lines 6-9. The string // denotes line 4 as comments. The line by line output code is visualized as below: int main() { int a, b, c; a = b + c; } Example 2: Input: source = ["a/comment", "line", "more_comment/b"] Output: ["ab"] Explanation: The original source string is "a/comment\nline\nmore_comment/b", where we have bolded the newline characters. After deletion, the implicit newline characters are deleted, leaving the string "ab", which when delimited by newline characters becomes ["ab"]. Constraints: 1 <= source.length <= 100 0 <= source[i].length <= 80 source[i] consists of printable ASCII characters. Every open block comment is eventually closed. There are no single-quote or double-quote in the input.

Explanation

• Iterate through each line of the source code. Maintain a boolean variable to track if we are currently inside a block comment.
  • For each line, iterate through the characters, checking for the start of a line comment ("//"), the start of a block comment ("/"), and the end of a block comment ("/").
  • Build a new line string by appending characters that are not part of any comment. Add the new line to the result if it's not empty after processing.

• Runtime Complexity: O(N*M), where N is the number of lines in the source code and M is the maximum length of a line.
• Space Complexity: O(N*M) in the worst case, to store the result.

Code

    def removeComments(source):
    result = []
    in_block_comment = False
    for line in source:
        new_line = ""
        i = 0
        while i < len(line):
            if in_block_comment:
                if i + 1 < len(line) and line[i:i+2] == "*/":
                    in_block_comment = False
                    i += 2
                else:
                    i += 1
            else:
                if i + 1 < len(line) and line[i:i+2] == "//":
                    break
                elif i + 1 < len(line) and line[i:i+2] == "/*":
                    in_block_comment = True
                    i += 2
                else:
                    new_line += line[i]
                    i += 1
        if new_line and not in_block_comment:
            result.append(new_line)
        elif new_line and in_block_comment:
            result.append(new_line) #Add this line in case block comment ends on a newline.

        elif new_line == "" and in_block_comment: # Check for special case when there is nothing to add at the end but still in block comment
            pass
        elif new_line == "" and not in_block_comment and len(result) > 0 and result[-1] == "": #check that result is not empty to avoid index error on [-1]
             pass# edge case if line is empty and we just went through a comment, ignore the line, prevent "" being added at end
        elif new_line and not in_block_comment and len(result) > 0 and result[-1] == "":#prevents adding a line if a previous line was already emtpy after comment removal
            result.append(new_line)

        elif new_line != "":

            result.append(new_line)


        elif new_line == "" and not in_block_comment:
             pass


    final_result = []

    for line in result:

        temp_line = ""
        i = 0
        in_block_comment = False

        while i < len(line):
                if in_block_comment:
                    if i + 1 < len(line) and line[i:i+2] == "*/":
                        in_block_comment = False
                        i += 2
                    else:
                        i += 1
                else:
                    if i + 1 < len(line) and line[i:i+2] == "//":
                        break
                    elif i + 1 < len(line) and line[i:i+2] == "/*":
                        in_block_comment = True
                        i += 2
                    else:
                        temp_line += line[i]
                        i += 1
        if temp_line != "":
                final_result.append(temp_line)




    return final_result