722.remove-comments.java

/*
 * @lc app=leetcode id=722 lang=java
 *
 * [722] Remove Comments
 *
 * https://leetcode.com/problems/remove-comments/description/
 *
 * algorithms
 * Medium (35.31%)
 * Likes:    374
 * Dislikes: 1033
 * Total Accepted:    34.6K
 * Total Submissions: 97.6K
 * Testcase Example:  '["/*Test program */", "int main()", "{ ", "  // variable declaration ", "int a, b, c;", "/* This is a test", "   multiline  ", "   comment for ", "   testing */", "a = b + c;", "}"]'
 *
 * 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.
 * 
 */

// @lc code=start
class Solution {
    public List<String> removeComments(String[] source) {
        List<String> list = new ArrayList<String>();
		StringBuilder sb = new StringBuilder();
		
		boolean mode = false;
		
		for(String s: source){
			for(int i=0;i<s.length();i++){
				if(mode){
					// if * is on
					if(s.charAt(i)=='*' && i<s.length()-1 && s.charAt(i+1)=='/'){
						mode = false;
						i++;
					}
				}
				else{
					if(s.charAt(i)=='/' && i<s.length()-1 && s.charAt(i+1)=='/'){
						break;
					}
					
					else if(s.charAt(i) == '/' && i<s.length()-1 && s.charAt(i+1)=='*'){
						mode = true;
						i++;
					}
					else
						sb.append(s.charAt(i));
				}
			}
			if(!mode && sb.length()>0){
				list.add(sb.toString());
				sb.setLength(0);
			}
		}
		
		return list;
    }
}
// @lc code=end