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 1:
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 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"].
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.

實現題。
每一行的內容都有剩出一部分有意義code，作為newLine加入到結果的潛力。掃描每行，分別檢索comment標誌符”/*”, “*/“, “//“來進行相關邏輯處理。同時用一個全局變量isInBlock記憶當前的狀態，是否在/**/裏，來幫助邏輯的處理。
1.如果現在isInBlock，那就只想著找到”*/“。
2.如果現在!isInBlock，如果找到”/*”，即反轉block狀態了；如果找到”//“，那這行剩下都沒用了；如果不是特殊標誌符，那把這個有意義的char for code加到當前行的結果上。
一行掃完後，如果發現這行有加有意義內容，就加入最終結果裏。

細節：
1.為了題目要求的a/*xxx, xxx, xxx*/c最後要拿到ac而不是a,c這種要求，要把newLine拿出去做全局變量，使得不同行可以放到結果的一行裏。創造新行和添加結果的時候都加點小花邊。
2.判斷兩個字符的時候註意一下邊界檢查。

實現：

class Solution {
    public List<String> removeComments(String[] source) {
        List<String> ans = new ArrayList<>();
        boolean isInBlock = false;
        String newLine = "";
        for (String line : source) {
            if (!isInBlock) newLine = "";
            
 
for (int i = 0; i < line.length(); i++) {
                if (!isInBlock && i + 1 < line.length() && line.substring(i, i + 2).equals("/*")) {
                    isInBlock = true;
                    i++;
                } else if (isInBlock && i + 1 < line.length() && line.substring(i, i + 2).equals("*/")) {
                    isInBlock = false;
                    i++;
                } else if (!isInBlock && i + 1 < line.length() && line.substring(i, i + 2).equals("//")) {
                    break;
                } else if (!isInBlock){
                    newLine += line.charAt(i);
                }
            }
            if (!isInBlock && newLine.length() > 0) {
                ans.add(newLine);
            }
        }
        return ans;
    }
}

leetcode722 - Remove Comments - medium