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Java-based LeetCode algorithm problem solutions, regularly updated
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package g0701_0800.s0722_remove_comments;

// #Medium #Array #String #2022_03_24_Time_1_ms_(80.24%)_Space_42.3_MB_(53.67%)

import java.util.ArrayList;
import java.util.List;

/**
 * 722 - Remove Comments\.
 *
 * Medium
 *
 * 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 `"{@literal /}*"` denotes a block comment, which represents that all characters until the next (non-overlapping) occurrence of `"*{@literal /}"` should be ignored. (Here, occurrences happen in reading order: line by line from left to right.) To be clear, the string `"{@literal /}*{@literal /}"` 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 `"{@literal /}*"` 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 = "{@literal /}* Not a comment. *{@literal /}";"` 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 `"{@literal /}*"` 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 = ["{@literal /}*Test program *{@literal /}", "int main()", "{ ", " // variable declaration ", "int a, b, c;", "{@literal /}* This is a test", " multiline ", " comment for ", " testing *{@literal /}", "a = b + c;", "}"]
 *
 * **Output:** ["int main()","{ "," ","int a, b, c;","a = b + c;","}"]
 *
 * **Explanation:** The line by line code is visualized as below: 
 *
 *     {@literal /}*Test program *{@literal /} 
 *     int main() { 
 *     // variable declaration 
 *     int a, b, c; 
 *     {@literal /}* This is a test 
 *     multiline comment 
 *     for testing *{@literal /} 
 *     a = b + c; 
 *     } 
 *     The string {@literal /}* 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:**
 *
 * **Input:** source = ["a{@literal /}*comment", "line", "more_comment*{@literal /}b"]
 *
 * **Output:** ["ab"]
 *
 * **Explanation:** The original source string is "a{@literal /}*comment\nline\nmore_comment*{@literal /}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 or double-quote in the input.
**/
@SuppressWarnings("java:S135")
public class Solution {
    public List removeComments(String[] source) {
        List result = new ArrayList<>();
        StringBuilder sb = new StringBuilder();
        boolean multiComment = false;
        for (String line : source) {
            int n = line.length();
            int index = 0;
            while (index < n) {
                char ch = line.charAt(index);
                if (!multiComment && ch == '/') {
                    index++;
                    if (index >= n) {
                        sb.append(ch);
                        continue;
                    }
                    if (line.charAt(index) == '/') {
                        break;
                    } else if (line.charAt(index) == '*') {
                        multiComment = true;
                    } else {
                        sb.append(ch).append(line.charAt(index));
                    }
                } else if (multiComment && ch == '*') {
                    index++;
                    if (index >= n) {
                        continue;
                    }
                    if (line.charAt(index) == '/') {
                        multiComment = false;
                    } else {
                        index--;
                    }
                } else if (!multiComment) {
                    sb.append(ch);
                }
                index++;
            }
            if (sb.length() > 0 && !multiComment) {
                result.add(sb.toString());
                sb.setLength(0);
            }
        }
        return result;
    }
}