Remove Comments Problem
Description
LeetCode Problem 722.
Given a C++ program, remove comments from it. The program source is an array of strings source 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 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:
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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:
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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 ordouble-quote in the input.
Sample C++ Code
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class Solution {
public:
/* The idea is to just separate it into 4 cases.
* 1. If the current character and next one forms a "//" and we are not in a block comment.
* It means we ignore the current line and just move on to the next line.
* 2. If the current character and next one forms a new block comment and we are not currently in a block comment.
* It means we can ignore all the next characters until we find a closing block comment.
* 3. If the current character and next one forms a closing block comment and we are currently still in a block comment.
* It means we close the block comment and continue appending characters to string as usual.
* 4. Else this is just a normal character, append it to our string.
* Everytime we hit a new line and we are not in a block comment currently, we can push the string into a vector of answer.
*/
vector<string> removeComments(vector<string>& source) {
vector<string> ans;
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())
ans.push_back(s), s.clear();
}
return ans;
}
};