Problem: Remove Comments

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.


Python solution:
import math
import itertools
import bisect
import collections
import string
import heapq
import functools
import sortedcontainers
from typing import List, Dict, Tuple, Iterator

class Solution:
  def removeComments(self, source: List[str]) -> List[str]:
    ans = []
    commenting = False
    modified = ''

    for line in source:
      i = 0
      while i < len(line):
        if i + 1 == len(line):
          if not commenting:
            modified += line[i]
          i += 1
          break
        twoChars = line[i:i + 2]
        if twoChars == '/*' and not commenting:
          commenting = True
          i += 2
        elif twoChars == '*/' and commenting:
          commenting = False
          i += 2
        elif twoChars == '//':
          if not commenting:
            break
          else:
            i += 2
        else:
          if not commenting:
            modified += line[i]
          i += 1
      if modified and not commenting:
        ans.append(modified)
        modified = ''

    return ans


Java solution:
class Solution {
  public List<String> removeComments(String[] source) {
    List<String> ans = new ArrayList<>();
    boolean commenting = false;
    StringBuilder modified = new StringBuilder();

    for (final String line : source) {
      for (int i = 0; i < line.length();) {
        if (i + 1 == line.length()) {
          if (!commenting)
            modified.append(line.charAt(i));
          ++i;
          break;
        }
        String twoChars = line.substring(i, i + 2);
        if (twoChars.equals("/*") && !commenting) {
          commenting = true;
          i += 2;
        } else if (twoChars.equals("*/") && commenting) {
          commenting = false;
          i += 2;
        } else if (twoChars.equals("//")) {
          if (!commenting)
            break;
          else
            i += 2;
        } else {
          if (!commenting)
            modified.append(line.charAt(i));
          ++i;
        }
      }
      if (modified.length() > 0 && !commenting) {
        ans.add(modified.toString());
        modified.setLength(0);
      }
    }

    return ans;
  }
}


C++ solution:
class Solution {
 public:
  vector<string> removeComments(vector<string>& source) {
    vector<string> ans;
    bool commenting = false;
    string modified;

    for (const string& line : source) {
      for (int i = 0; i < line.length();) {
        if (i + 1 == line.length()) {
          if (!commenting)
            modified += line[i];
          ++i;
          break;
        }
        const string& twoChars = line.substr(i, 2);
        if (twoChars == "/*" && !commenting) {
          commenting = true;
          i += 2;
        } else if (twoChars == "*/" && commenting) {
          commenting = false;
          i += 2;
        } else if (twoChars == "//") {
          if (!commenting)
            break;
          else
            i += 2;
        } else {
          if (!commenting)
            modified += line[i];
          ++i;
        }
      }
      if (modified.length() > 0 && !commenting) {
        ans.push_back(modified);
        modified = "";
      }
    }

    return ans;
  }
};