HTML Elements

ardallie · ardallie · commit 3ff032c09a5c · 2021-08-17T00:52:34.000+01:00
diff --git a/src/medium/HtmlElements.java b/src/medium/HtmlElements.java
@@ -0,0 +1,119 @@
+package medium;
+
+import java.util.Stack;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+
+/**
+ * Have the function HTMLElements(str) read the str parameter being passed
+ * which will be a string of HTML DOM elements and plain text.
+ * ---
+ * The elements that will be used are: b, i, em, div, p.
+ * For example: if str is "<div><b><p>hello world</p></b></div>" then this string of DOM elements
+ * is nested correctly so your program should return the string true.
+ * ---
+ * If a string is not nested correctly, return the first element encountered where,
+ * if changed into a different element, would result in a properly formatted string.
+ * ---
+ * If the string is not formatted properly,
+ * then it will only be one element that needs to be changed.
+ * For example: if str is "<div><i>hello</i>world</b>"
+ * then your program should return the string div
+ * because if the first <div> element were changed into a <b>,
+ * the string would be properly formatted.
+ */
+public class HtmlElements {
+
+  /**
+   * A stack helps to determine if elements are nested correctly.
+   */
+  private static final Stack<String> stack = new Stack<>();
+
+  /**
+   * Process a string to prepare for further inspection.
+   * 1. convert to lowercase
+   * 2. remove text content between tags
+   * 3. add spaces between tags
+   * 4. remove multiple spaces
+   * 5. trim (remove leading and trailing spaces)
+   * 6. split to array of strings
+   *
+   * @param str input string
+   * @return parsed string
+   */
+  private static String[] parseElements(String str) {
+    return str
+        .toLowerCase()
+        .replaceAll(">[^<]+", ">")
+        .replaceAll("([>])(?=[<])", "$1 ")
+        .replaceAll(" +", " ")
+        .trim().split(" ");
+  }
+
+  /**
+   * Checks if a string is an opening tag.
+   *
+   * @param tag a string to check
+   * @return true if a string is an opening tag
+   */
+  private static boolean isOpeningTag(String tag) {
+    Pattern pattern = Pattern.compile("<[a-z]>|<[a-z][a-z1-9]+>");
+    Matcher matcher = pattern.matcher(tag);
+    return matcher.find();
+  }
+
+  /**
+   * Checks if a string is an closing tag.
+   *
+   * @param tag a string to check
+   * @return true if a string is a closing tag
+   */
+  private static boolean isClosingTag(String tag) {
+    Pattern pattern = Pattern.compile("</[a-z]>|</[a-z][a-z1-9]+>");
+    Matcher matcher = pattern.matcher(tag);
+    return matcher.find();
+  }
+
+  /**
+   * Get an enclosed value.
+   *
+   * @param tag input tag with angle brackets
+   * @return the enclosed value of a tag
+   */
+  private static String getTagValue(String tag) {
+    return tag.replaceAll("[></]", "");
+  }
+
+  /**
+   * HTML Elements function.
+   *
+   * @param str input string
+   * @return "true" if elements are nested correctly, or an enclosed tag value if not.
+   */
+  private static String htmlElements(String str) {
+    String[] parsedTags = parseElements(str);
+    for (String tag : parsedTags) {
+      if (isOpeningTag(tag)) {
+        stack.push(tag);
+      } else if (isClosingTag(tag) && !stack.isEmpty()) {
+        if (getTagValue(stack.peek()).equals(getTagValue(tag))) {
+          stack.pop();
+        }
+      }
+    }
+    return stack.isEmpty() ? "true" : getTagValue(stack.peek());
+  }
+
+  /**
+   * Entry point.
+   *
+   * @param args command line arguments
+   */
+  public static void main(String[] args) {
+    String result1 = htmlElements("<div><b><p>hello world</p></b></div>");
+    System.out.println(result1);
+    String result2 = htmlElements("<div><b><p>hello world</b></div>");
+    System.out.println(result2);
+  }
+
+}
