No1410.html-entity-parser.cs

/*
 * Difficulty:
 * Medium
 *
 * Desc:
 * HTML entity parser is the parser that takes HTML code as input and replace all the entities of the special characters by the characters itself.
 *
 * The special characters and their entities for HTML are:
 * - Quotation Mark: the entity is " and symbol character is ".
 * - Single Quote Mark: the entity is ' and symbol character is '.
 * - Ampersand: the entity is & and symbol character is &.
 * - Greater Than Sign: the entity is > and symbol character is >.
 * - Less Than Sign: the entity is &lt; and symbol character is <.
 * - Slash: the entity is &frasl; and symbol character is /.
 *
 * Given the input text string to the HTML parser, you have to implement the entity parser.
 * Return the text after replacing the entities by the special characters.
 *
 * Example 1:
 * Input: text = "&amp; is an HTML entity but &ambassador; is not."
 * Output: "& is an HTML entity but &ambassador; is not."
 * Explanation: The parser will replace the &amp; entity by &
 *
 * Example 2:
 * Input: text = "and I quote: &quot;...&quot;"
 * Output: "and I quote: \"...\""
 *
 * Example 3:
 * Input: text = "Stay home! Practice on Leetcode :)"
 * Output: "Stay home! Practice on Leetcode :)"
 *
 * Example 4:
 * Input: text = "x &gt; y &amp;&amp; x &lt; y is always false"
 * Output: "x > y && x < y is always false"
 *
 * Example 5:
 * Input: text = "leetcode.com&frasl;problemset&frasl;all"
 * Output: "leetcode.com/problemset/all"
 *
 * Constraints:
 * 1 <= text.length <= 10^5
 * The string may contain any possible characters out of all the 256 ASCII characters.
*/

public class Solution {
    public string EntityParser(string text) {
        List<string> arr = new List<string>();
        Dictionary<string, string> dict = new Dictionary<string, string>() {
            { "&quot;", "\"" },
            { "&apos;", "'" },
            { "&amp;", "&" },
            { "&gt;", ">" },
            { "&lt;", "<" },
            { "&frasl;", "/" }
        };

        int i = 0;
        while (i < text.Length) {
            if (text[i] == '&') {
                int j = i;
                while (i < text.Length && text[i] != ';') i += 1;
                if (dict.ContainsKey(text.Substring(j, i - j + 1))) {
                    arr.Add(dict[text.Substring(j, i - j + 1)]);
                } else {
                    arr.Add(text.Substring(j, i - j + 1));
                }
            } else {
                arr.Add(text[i].ToString());
            }
            i += 1;
        }
        return string.Join("", arr);
    }
}