{ "data": { "question": { "questionId": "591", "questionFrontendId": "591", "boundTopicId": null, "title": "Tag Validator", "titleSlug": "tag-validator", "content": "

Given a string representing a code snippet, implement a tag validator to parse the code and return whether it is valid.

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A code snippet is valid if all the following rules hold:

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    \n\t
  1. The code must be wrapped in a valid closed tag. Otherwise, the code is invalid.
  2. \n\t
  3. A closed tag (not necessarily valid) has exactly the following format : <TAG_NAME>TAG_CONTENT</TAG_NAME>. Among them, <TAG_NAME> is the start tag, and </TAG_NAME> is the end tag. The TAG_NAME in start and end tags should be the same. A closed tag is valid if and only if the TAG_NAME and TAG_CONTENT are valid.
  4. \n\t
  5. A valid TAG_NAME only contain upper-case letters, and has length in range [1,9]. Otherwise, the TAG_NAME is invalid.
  6. \n\t
  7. A valid TAG_CONTENT may contain other valid closed tags, cdata and any characters (see note1) EXCEPT unmatched <, unmatched start and end tag, and unmatched or closed tags with invalid TAG_NAME. Otherwise, the TAG_CONTENT is invalid.
  8. \n\t
  9. A start tag is unmatched if no end tag exists with the same TAG_NAME, and vice versa. However, you also need to consider the issue of unbalanced when tags are nested.
  10. \n\t
  11. A < is unmatched if you cannot find a subsequent >. And when you find a < or </, all the subsequent characters until the next > should be parsed as TAG_NAME (not necessarily valid).
  12. \n\t
  13. The cdata has the following format : <![CDATA[CDATA_CONTENT]]>. The range of CDATA_CONTENT is defined as the characters between <![CDATA[ and the first subsequent ]]>.
  14. \n\t
  15. CDATA_CONTENT may contain any characters. The function of cdata is to forbid the validator to parse CDATA_CONTENT, so even it has some characters that can be parsed as tag (no matter valid or invalid), you should treat it as regular characters.
  16. \n
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Example 1:

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\nInput: code = "<DIV>This is the first line <![CDATA[<div>]]></DIV>"\nOutput: true\nExplanation: \nThe code is wrapped in a closed tag : <DIV> and </DIV>. \nThe TAG_NAME is valid, the TAG_CONTENT consists of some characters and cdata. \nAlthough CDATA_CONTENT has an unmatched start tag with invalid TAG_NAME, it should be considered as plain text, not parsed as a tag.\nSo TAG_CONTENT is valid, and then the code is valid. Thus return true.\n
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Example 2:

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\nInput: code = "<DIV>>>  ![cdata[]] <![CDATA[<div>]>]]>]]>>]</DIV>"\nOutput: true\nExplanation:\nWe first separate the code into : start_tag|tag_content|end_tag.\nstart_tag -> "<DIV>"\nend_tag -> "</DIV>"\ntag_content could also be separated into : text1|cdata|text2.\ntext1 -> ">>  ![cdata[]] "\ncdata -> "<![CDATA[<div>]>]]>", where the CDATA_CONTENT is "<div>]>"\ntext2 -> "]]>>]"\nThe reason why start_tag is NOT "<DIV>>>" is because of the rule 6.\nThe reason why cdata is NOT "<![CDATA[<div>]>]]>]]>" is because of the rule 7.\n
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Example 3:

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\nInput: code = "<A>  <B> </A>   </B>"\nOutput: false\nExplanation: Unbalanced. If "<A>" is closed, then "<B>" must be unmatched, and vice versa.\n
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Constraints:

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This is the first line ]]>
\"\n\"
>> ![cdata[]] ]>]]>]]>>]
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Compiled with clang 11 using the latest C++ 17 standard.

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Your code is compiled with level two optimization (-O2). AddressSanitizer is also enabled to help detect out-of-bounds and use-after-free bugs.

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Most standard library headers are already included automatically for your convenience.

\"], \"java\": [\"Java\", \"

OpenJDK 17 . Java 8 features such as lambda expressions and stream API can be used.

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Most standard library headers are already included automatically for your convenience.

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Includes Pair class from https://docs.oracle.com/javase/8/javafx/api/javafx/util/Pair.html.

\"], \"python\": [\"Python\", \"

Python 2.7.12.

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Most libraries are already imported automatically for your convenience, such as array, bisect, collections. If you need more libraries, you can import it yourself.

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For Map/TreeMap data structure, you may use sortedcontainers library.

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Note that Python 2.7 will not be maintained past 2020. For the latest Python, please choose Python3 instead.

\"], \"c\": [\"C\", \"

Compiled with gcc 8.2 using the gnu99 standard.

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Your code is compiled with level one optimization (-O1). AddressSanitizer is also enabled to help detect out-of-bounds and use-after-free bugs.

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Most standard library headers are already included automatically for your convenience.

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For hash table operations, you may use uthash. \\\"uthash.h\\\" is included by default. Below are some examples:

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1. Adding an item to a hash.\\r\\n

\\r\\nstruct hash_entry {\\r\\n    int id;            /* we'll use this field as the key */\\r\\n    char name[10];\\r\\n    UT_hash_handle hh; /* makes this structure hashable */\\r\\n};\\r\\n\\r\\nstruct hash_entry *users = NULL;\\r\\n\\r\\nvoid add_user(struct hash_entry *s) {\\r\\n    HASH_ADD_INT(users, id, s);\\r\\n}\\r\\n
\\r\\n

\\r\\n\\r\\n

2. Looking up an item in a hash:\\r\\n

\\r\\nstruct hash_entry *find_user(int user_id) {\\r\\n    struct hash_entry *s;\\r\\n    HASH_FIND_INT(users, &user_id, s);\\r\\n    return s;\\r\\n}\\r\\n
\\r\\n

\\r\\n\\r\\n

3. Deleting an item in a hash:\\r\\n

\\r\\nvoid delete_user(struct hash_entry *user) {\\r\\n    HASH_DEL(users, user);  \\r\\n}\\r\\n
\\r\\n

\"], \"csharp\": [\"C#\", \"

C# 10 with .NET 6 runtime

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Your code is compiled with debug flag enabled (/debug).

\"], \"javascript\": [\"JavaScript\", \"

Node.js 16.13.2.

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Your code is run with --harmony flag, enabling new ES6 features.

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lodash.js library is included by default.

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For Priority Queue / Queue data structures, you may use datastructures-js/priority-queue and datastructures-js/queue.

\"], \"ruby\": [\"Ruby\", \"

Ruby 3.1

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Some common data structure implementations are provided in the Algorithms module: https://www.rubydoc.info/github/kanwei/algorithms/Algorithms

\"], \"swift\": [\"Swift\", \"

Swift 5.5.2.

\"], \"golang\": [\"Go\", \"

Go 1.17.6.

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Support https://godoc.org/github.com/emirpasic/gods library.

\"], \"python3\": [\"Python3\", \"

Python 3.10.

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Most libraries are already imported automatically for your convenience, such as array, bisect, collections. If you need more libraries, you can import it yourself.

\\r\\n\\r\\n

For Map/TreeMap data structure, you may use sortedcontainers library.

\"], \"scala\": [\"Scala\", \"

Scala 2.13.7.

\"], \"kotlin\": [\"Kotlin\", \"

Kotlin 1.3.10.

\"], \"rust\": [\"Rust\", \"

Rust 1.58.1

\\r\\n\\r\\n

Supports rand v0.6\\u00a0from crates.io

\"], \"php\": [\"PHP\", \"

PHP 8.1.

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With bcmath module

\"], \"typescript\": [\"Typescript\", \"

TypeScript 4.5.4, Node.js 16.13.2.

\\r\\n\\r\\n

Your code is run with --harmony flag, enabling new ES2020 features.

\\r\\n\\r\\n

lodash.js library is included by default.

\"], \"racket\": [\"Racket\", \"

Run with Racket 8.3.

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