Here, We see Tag Validator LeetCode Solution. This Leetcode problem is done in many programming languages like C++, Java, JavaScript, Python, etc. with different approaches.
List of all LeetCode Solution
Tag Validator LeetCode Solution
Table of Contents
Problem Statement
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:
- The code must be wrapped in a valid closed tag. Otherwise, the code is invalid.
- 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. - A valid
TAG_NAMEonly contain upper-case letters, and has length in range [1,9]. Otherwise, theTAG_NAMEis invalid. - A valid
TAG_CONTENTmay 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, theTAG_CONTENTis invalid. - 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.
- 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). - The cdata has the following format :
<![CDATA[CDATA_CONTENT]]>. The range ofCDATA_CONTENTis defined as the characters between<![CDATA[and the first subsequent]]>. CDATA_CONTENTmay contain any characters. The function of cdata is to forbid the validator to parseCDATA_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 = “<DIV>This is the first line <![CDATA[<div>]]></DIV>”
Output: true
Explanation: The code is wrapped in a closed tag : <DIV> and </DIV>. 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 = “<DIV>>> ![cdata[]] <![CDATA[<div>]>]]>]]>>]</DIV>”
Output: true
Explanation: We first separate the code into : start_tag|tag_content|end_tag. start_tag -> “<DIV>” end_tag -> “</DIV>” tag_content could also be separated into : text1|cdata|text2. text1 -> “>> ![cdata[]] “ cdata -> “<![CDATA[<div>]>]]>”, where the CDATA_CONTENT is “<div>]>” text2 -> “]]>>]” The reason why start_tag is NOT “<DIV>>>” is because of the rule 6. The reason why cdata is NOT “<![CDATA[<div>]>]]>]]>” is because of the rule 7.
Example 3:
Input: code = “<A> <B> </A> </B>”
Output: false
Explanation: Unbalanced. If “<A>” is closed, then “<B>” must be unmatched, and vice versa.
Tag Validator LeetCode Solution C++
class Solution {
public:
bool isValid(string code) {
int i = 0;
return validTag(code, i) && i == code.size();
}
private:
bool validTag(string s, int& i) {
int j = i;
string tag = parseTagName(s, j);
if (tag.empty()) return false;
if (!validContent(s, j)) return false;
int k = j + tag.size() + 2; // expecting j = pos of "</" , k = pos of '>'
if (k >= s.size() || s.substr(j, k + 1 - j) != "</" + tag + ">") return false;
i = k + 1;
return true;
}
string parseTagName(string s, int& i) {
if (s[i] != '<') return "";
int j = s.find('>', i);
if (j == string::npos || j - 1 - i < 1 || 9 < j - 1 - i) return "";
string tag = s.substr(i + 1, j - 1 - i);
for (char ch : tag) {
if (ch < 'A' || 'Z' < ch) return "";
}
i = j + 1;
return tag;
}
bool validContent(string s, int& i) {
int j = i;
while (j < s.size()) {
if (!validText(s, j) && !validCData(s, j) && !validTag(s, j)) break;
}
i = j;
return true;
}
bool validText(string s, int& i) {
int j = i;
while (i < s.size() && s[i] != '<') { i++; }
return i != j;
}
bool validCData(string s, int& i) {
if (s.find("<![CDATA[", i) != i) return false;
int j = s.find("]]>", i);
if (j == string::npos) return false;
i = j + 3;
return true;
}
};Code language: PHP (php)Tag Validator LeetCode Solution Java
class Solution {
public boolean isValid(String code) {
int length = code.length();
Stack S=new Stack();
for (int i = 0; i < length; i++) {
if(i>0 && S.empty())
return false;
if(code.startsWith("<![CDATA[",i)){
int pos=code.indexOf("]]>",i+9);
if (pos==-1)
return false;
else
i=pos+2;
}
else if(code.startsWith("</",i)){
int pos=code.indexOf('>',i+2);
if (pos==-1) {
return false;
}
String to_be_matched=code.substring(i+2,pos);
if(S.empty())
return false;
if(!to_be_matched.equals((String)S.pop()))
return false;
i=pos;
}
else if (code.charAt(i) == '<') {
int pos=code.indexOf('>',i+1);
if (pos==-1)
return false;
String to_be_pushed=code.substring(i+1, pos);
if(!(to_be_pushed.length() >=1 && to_be_pushed.length() <=9))
return false;
for(int k=0;k<to_be_pushed.length();k++) {
char temp = to_be_pushed.charAt(k);
if (!(temp >= 65 && temp <= 90))
return false;
}
S.push(to_be_pushed);
i=pos;
}
else
{
int pos=code.indexOf('<',i);
if (pos!=-1) {
i=pos-1;
}
}
}
if(S.empty())
return true;
else
return false;
}
}Code language: JavaScript (javascript)Tag Validator LeetCode Solution JavaScript
var isValid = function(code) {
if (code === 't') return false;
while (/<!\[CDATA\[.*?\]\]>/.test(code)) {
code = code.replace(/<!\[CDATA\[.*?\]\]>/g, 'c');
}
while (/<([A-Z]{1,9})>([^<]*)<\/(\1)>/.test(code)) {
code = code.replace(/<([A-Z]{1,9})>([^<]*)<\/(\1)>/g, 't');
}
return code === 't';
};Code language: JavaScript (javascript)Tag Validator LeetCode Solution Python
class Solution(object):
def isValid(self, code):
code = code.replace("<![CDATA[", "?")
if code[0] == "?": return False
n = len(code)
stack = []
i = 0
while i < n:
if code[i] == "<":
isClosingTag = False
tagName = []
i += 1
if i < n and code[i] == "/":
isClosingTag = True
i += 1
while i < n and code[i] != ">":
tagName.append(code[i])
i += 1
if len(tagName) < 1 or len(tagName) > 9: return False
tagName = "".join(tagName)
if tagName.isalpha() and tagName.isupper():
if isClosingTag:
if stack and stack[-1] == tagName:
stack.pop()
if i != n - 1 and not stack: return False
else: return False
else: stack.append(tagName)
else: return False
elif code[i] == "?":
i += 1
while (i + 2 < n) and not (code[i] == "]" and code[i + 1] == "]" and code[i + 2] == ">"): i += 1
if i + 2 < n and code[i] == "]" and code[i + 1] == "]" and code[i + 2] == ">": i += 3
else:
if i != n - 1 and not stack: return False
i += 1
return not stack