722. Remove Comments

问题描述：

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  .

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
line
more_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.

解题思路：

这道题让我们去除代码中的注释语句，并且标注没有单引号和双引号的出现，即代表只要出现的“//”和“/*”都会是有效的注释语句

同时/*一定会有与之匹配的*/

所以我们可以逐行检查。

用一个bool值来记录这句话是否在一个注释块中

用一个新的字符串s来存储这一行会出现的语句：

　　1.当遇见"//"且不再注释块中时，则将后面的句子全部抛弃

　　2.当遇见“/*”且不在注释块中时，标识bool值为true并且直接越过‘*’开始检查后面的句子

　　3.当遇见“*/”且在注释块中时，标识bool值为false并且越过‘/’开始检查后面的句子

　　4.当标识块为false且以上情况都没有遇见的时候，将该字符加入s

对每一句话处理完后，都要将非空的s加入返回数组，并且将s重置为空

代码：

class Solution {
public:
    vector<string> removeComments(vector<string>& source) {
        vector<string> ret;
        string s;
        bool comment = false;
        for(int i = 0; i < source.size(); i++){
            for(int j = 0; j < source[i].size(); j++){
                if(!comment && j + 1 < source[i].size() && source[i][j] == '/' && source[i][j+1] == '/') break;
                else if(!comment && j + 1 < source[i].size() && source[i][j] == '/' && source[i][j+1] == '*'){
                    comment = true;
                    j++;
                }else if(comment && j + 1 < source[i].size() && source[i][j] == '*' && source[i][j+1] == '/'){
                    comment = false;
                    j++;
                }else if(!comment) s.push_back(source[i][j]);
            }
            if(!comment && s.size() != 0){
                ret.push_back(s);
                s.clear();
            }
        }
        return ret;
    }
};