Package g0501_0600.s0591_tag_validator

Class Solution

  • public class Solution
extends Object
    591 - Tag Validator\. Hard Given a string representing a code snippet, implement a tag validator to parse the code and return whether it is valid. A code snippet is valid if all the following rules hold: 1. The code must be wrapped in a **valid closed tag**. Otherwise, the code is invalid. 2. A **closed tag** (not necessarily valid) has exactly the following format : `TAG_CONTENT`. Among them, `` is the start tag, and `` 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. 3. A **valid** `TAG_NAME` only contain **upper-case letters** , and has length in range [1,9]. Otherwise, the `TAG_NAME` is **invalid**. 4. 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**. 5. 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. 6. A `<` is unmatched if you cannot find a subsequent `>`. And when you find a `<` or `` should be parsed as TAG\_NAME (not necessarily valid). 7. The cdata has the following format : ``. The range of `CDATA_CONTENT` is defined as the characters between ``. 8. `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**. **Example 1:** **Input:** code = "
    This is the first line ]]>
    " **Output:** true **Explanation:** The code is wrapped in a closed tag :
    and
    . The TAG_NAME is valid, the TAG_CONTENT consists of some characters and cdata. Although CDATA_CONTENT has an unmatched start tag with invalid TAG_NAME, it should be considered as plain text, not parsed as a tag. So TAG_CONTENT is valid, and then the code is valid. Thus return true. **Example 2:** **Input:** code = "
    >> ![cdata[]] ]>]]>]]>>]
    " **Output:** true **Explanation:** We first separate the code into : start_tag|tag_content|end_tag. start_tag -> "
    " end_tag -> "
    " tag_content could also be separated into : text1|cdata|text2. text1 -> ">> ![cdata[]] " cdata -> "]>]]>", where the CDATA_CONTENT is "
    ]>" text2 -> "]]>>]" The reason why start_tag is NOT "
    >>" is because of the rule 6. The reason why cdata is NOT "]>]]>]]>" is because of the rule 7. **Example 3:** **Input:** code = " " **Output:** false **Explanation:** Unbalanced. If "" is closed, then "" must be unmatched, and vice versa. **Constraints:** * `1 <= code.length <= 500` * `code` consists of English letters, digits, `'<'`, `'>'`, `'/'`, `'!'`, `'['`, `']'`, `'.'`, and `' '`.

    • Constructor Detail

      • Solution

        public Solution()

    • Method Detail

      • isValid

        public boolean isValid​(String code)