<p><strong>HTML entity parser</strong> is the parser that takes HTML code as input and replace all the entities of the special characters by the characters itself.</p>

<p>The special characters and their entities for HTML are:</p>

<ul>
	<li><strong>Quotation Mark:</strong> the entity is <code>&amp;quot;</code> and symbol character is <code>&quot;</code>.</li>
	<li><strong>Single Quote Mark:</strong> the entity is <code>&amp;apos;</code> and symbol character is <code>&#39;</code>.</li>
	<li><strong>Ampersand:</strong> the entity is <code>&amp;amp;</code> and symbol character is <code>&amp;</code>.</li>
	<li><strong>Greater Than Sign:</strong> the entity is <code>&amp;gt;</code> and symbol character is <code>&gt;</code>.</li>
	<li><strong>Less Than Sign:</strong> the entity is <code>&amp;lt;</code> and symbol character is <code>&lt;</code>.</li>
	<li><strong>Slash:</strong> the entity is <code>&amp;frasl;</code> and symbol character is <code>/</code>.</li>
</ul>

<p>Given the input <code>text</code> string to the HTML parser, you have to implement the entity parser.</p>

<p>Return <em>the text after replacing the entities by the special characters</em>.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>

<pre>
<strong>Input:</strong> text = &quot;&amp;amp; is an HTML entity but &amp;ambassador; is not.&quot;
<strong>Output:</strong> &quot;&amp; is an HTML entity but &amp;ambassador; is not.&quot;
<strong>Explanation:</strong> The parser will replace the &amp;amp; entity by &amp;
</pre>

<p><strong class="example">Example 2:</strong></p>

<pre>
<strong>Input:</strong> text = &quot;and I quote: &amp;quot;...&amp;quot;&quot;
<strong>Output:</strong> &quot;and I quote: \&quot;...\&quot;&quot;
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>1 &lt;= text.length &lt;= 10<sup>5</sup></code></li>
	<li>The string may contain any possible characters out of all the 256 ASCII characters.</li>
</ul>

class Solution {
public:
    string entityParser(string text) {
        std::unordered_map<std::string, char> sc {
            {"&quot;", '"'},
            {"&apos;", '\''},
            {"&amp;", '&'},
            {"&gt;", '>'},
            {"&lt;", '<'},
            {"&frasl;", '/'},
        };

        std::stringstream ss;

        int i = 0;
        int n = text.length();

        while (i < n) {
            if (text[i] != '&') {
                ss << text[i];
                ++i;
                continue;
            }

            std::string tmp = "&";
            ++i;

            while (i < n) {
                if (text[i] == ';') {
                    tmp += ';';
                    auto it = sc.find(tmp);

                    if (it != sc.end()) {
                        ss << it->second;
                    } else {
                        ss << tmp;
                    }

                    break;
                } else if (text[i] == '&') {
                    ss << tmp;
                    tmp = '&';
                } else {
                    tmp += text[i];
                }
                ++i;
            }

            if (tmp[tmp.length()-1] != ';') {
                ss << tmp;
            } 

            ++i;
        }

        return ss.str();
    }
};
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