722.RemoveComments.py

'''
    Given a C++ program, remove comments from it. The program 
    source is an array where source[i] is the i-th 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 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: 
    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:
    Input: 
    source = ["/*Test program */", 
            "int main()", 
            "{ ", 
            "  // variable declaration ", 
            "int a, b, c;", 
            "/* This is a test", 
            "   multiline  ", 
            "   comment for ", 
            "   testing */", 
            "a = b + c;", 
            "}"]

    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;
            }

    Output: ["int main()","{ ","  ","int a, b, c;","a = b + c;","}"]

    The line by line code is visualized as below:
            int main()
            { 
            
            int a, b, c;
            a = b + c;
            }

    Explanation: The string /* denotes a block comment, 
                 including line 1 and lines 6-9. 
                 The string // denotes line 4 as comments.

    Example:
    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"].

    Note:
        - The length of source is in the range [1, 100].
        - The length of source[i] is in the range [0, 80].
        - Every open block comment is eventually closed.
        - There are no single-quote, double-quote, or 
          control characters in the source code.
'''
#Difficulty: Medium
#53 / 53 test cases passed.
#Runtime: 24 ms
#Memory Usage: 14.5 MB

#Runtime: 24 ms, faster than 95.20% of Python3 online submissions for Remove Comments.
#Memory Usage: 14.5 MB, less than 13.20% of Python3 online submissions for Remove Comments.

class Solution:
    def removeComments(self, source: List[str]) -> List[str]:
        i = 1
        source_string = '\n'.join(source) + '\n'

        while i < len(source_string):

            # comment /* */
            if source_string[i-1: i+1] == '/*':
                j = i + 1
                while source_string[j: j+2] != '*/':
                    j += 1
                if source_string[j: j+2] == '*/':
                    source_string = source_string[:i-1] + source_string[j+2:]
                    continue

            # comment //
            if source_string[i-1: i+1] == '//':
                j = i + 1
                while source_string[j] != '\n':
                    j += 1
                if source_string[j] == '\n':
                    source_string = source_string[:i-1] + source_string[j:]

            i += 1

        return [val for val in source_string.split('\n') if val]