src/main/java/BonusExercises.java

@@ -20,11 +20,27 @@ public class BonusExercises {
             - Each segment (between dots) must follow same hyphen rules
      */
     public boolean validateEmail(String email) {
-        String regex = ""; // todo
+        if (email == null) return false;
-        Pattern pattern = Pattern.compile(regex);
-        Matcher matcher = pattern.matcher(email);
 
-        return matcher.matches();
+        // Explanation:
+        // ^ start
+        // (?!\\.)           - cannot start with dot
+        // (?!.*\\.{2})      - cannot contain consecutive dots
+        // [A-Za-z0-9._%+-]+ - allowed local chars
+        // (?<!\\.)          - cannot end with dot
+        // @
+        // (?!-)[A-Za-z0-9-]+(?<!-) - first domain label, no leading/trailing hyphen
+        // (?:\\.(?!-)[A-Za-z0-9-]+(?<!-))* - other domain labels same rule
+        // $ end
+        //
+        // rejects underscores in domain labels
+        String regex = "^(?!\\.)" +
+                "(?!.*\\.{2})" +
+                "[A-Za-z0-9._%+-]+" +
+                "(?<!\\.)@" +
+                "(?!-)[A-Za-z0-9-]+(?<!-)(?:\\.(?!-)[A-Za-z0-9-]+(?<!-))*$";
+
+        return email.matches(regex);
     }
 
     /*
@@ -38,39 +54,119 @@ public class BonusExercises {
 
         If no match for a date is found in the string, return null.
     */
-    public String findDate(String string) {
+    public String findDate(String string)
-        // todo
+    {
+        if (string == null)
+            return null;
+
+        String day = "(0[1-9]|[12][0-9]|3[01])";
+        String month = "(0[1-9]|1[0-2])";
+        String year = "\\d{4}";
+
+        String regex =
+                "\\b(?:" +
+                        year + "-" + month + "-" + day +      // YYYY-MM-DD
+                        "|" +
+                        year + "/" + month + "/" + day +      // YYYY/MM/DD
+                        "|" +
+                        day + "/" + month + "/" + year +      // DD/MM/YYYY
+                        "|" +
+                        month + "/" + day + "/" + year +      // MM/DD/YYYY
+                        ")\\b";
+
+        Pattern pattern = Pattern.compile(regex);
+        Matcher matcher = pattern.matcher(string);
+
+        if (matcher.find())
+            return matcher.group();
+
         return null;
     }
 
-    /*
-        given a string, implement the method to detect all valid passwords
-        then, it should return the count of them
 
-        a valid password has the following properties:
+    /*
-        - at least 8 characters
+           given a string, implement the method to detect all valid passwords
-        - has to include at least one uppercase letter, and at least a lowercase
+           then, it should return the count of them
-        - at least one number and at least a special char "!@#$%^&*"
+
-        - has no white-space in it
+           a valid password has the following properties:
-     */
+           - at least 8 characters
-    public int findValidPasswords(String string) {
+           - has to include at least one uppercase letter, and at least a lowercase
-        // todo
+           - at least one number and at least a special char "!@#$%^&*"
-        return -1;
+           - has no white-space in it
+    */
+    public int findValidPasswords(String string)
+    {
+        if (string == null || string.isEmpty())
+            return 0;
+
+        // Regex for a valid password based on the specified conditions:
+        // ^                     - Start of the string
+        // (?=.*[A-Z])          - Positive lookahead for at least one uppercase letter
+        // (?=.*[a-z])          - Positive lookahead for at least one lowercase letter
+        // (?=.*\\d)            - Positive lookahead for at least one digit (\\d is equivalent to [0-9])
+        // (?=.*[!@#$%^&*])     - Positive lookahead for at least one special character from the set
+        // \\S{8,}               - Matches at least 8 non-whitespace characters
+        // $                     - End of the string
+        String passwordRegex = "^(?=.*[A-Z])(?=.*[a-z])(?=.*\\d)(?=.*[!@#$%^&*])\\S{8,}$";
+
+        Pattern passwordPattern = Pattern.compile(passwordRegex);
+
+        int validPasswordCount = 0;
+
+        // Split the input text into potential password tokens.
+        // \\S+ matches one or more non-whitespace characters.
+        Matcher tokenMatcher = Pattern.compile("\\S+").matcher(string);
+
+        while (tokenMatcher.find()) {
+            String potentialPassword = tokenMatcher.group();
+
+            // The prompt implies that tokens from the input string are directly considered as passwords.
+            // If there was a need to strip leading/trailing punctuation as in the previous context,
+            // that logic would go here. However, based on the current prompt, we use the token as-is.
+
+            if (passwordPattern.matcher(potentialPassword).matches()) {
+                validPasswordCount++;
+            }
+        }
+
+        return validPasswordCount;
     }
 
+
     /*
         you should return a list of *words* which are palindromic
         by word we mean at least 3 letters with no whitespace in it
 
-        note: your implementation should be case-insensitive, e.g. Aba -> is palindrome
+       note: your implementation should be case-insensitive, e.g. Aba -> is palindrome
-     */
+    */
-    public List<String> findPalindromes(String string) {
+    public List<String> findPalindromes(String string)
+    {
         List<String> list = new ArrayList<>();
-        // todo
+        if (string == null) return list;
+
+        Matcher matcher = Pattern.compile("\\b[A-Za-z]{3,}\\b").matcher(string);
+
+        while (matcher.find())
+        {
+            String word = matcher.group();
+
+            boolean isPalindrome = new StringBuilder(word).reverse().toString().equalsIgnoreCase(word);
+
+            if (isPalindrome)
+                list.add(word);
+        }
+
         return list;
     }
 
     public static void main(String[] args) {
-        // you can test your code here
+        BonusExercises b = new BonusExercises();
+
+        System.out.println(b.validateEmail("user.name+tag@sub-domain.co.uk")); // true
+        System.out.println(b.validateEmail(".bad@domain.com"));                 // false
+        System.out.println(b.findDate("Today's date is 2024-07-15."));         // 2024-07-15
+        System.out.println(b.findDate("event on 12/09/2023 in US format"));    // 12/09/2023
+        System.out.println(b.findValidPasswords("Abcdef1! strongP@ss2 WeakPass noSpacePass3!"));
+        System.out.println(b.findPalindromes("Level noon Kayak test civic radar rotor deed pop"));
     }
 }

src/main/java/MainExercises.java

@@ -1,3 +1,6 @@
+import java.util.ArrayList;
+import java.util.List;
+
 public class MainExercises
 {
     /*
@@ -18,15 +21,33 @@ public class MainExercises
 
     the output has to be a two-dimensional array of characters, so don't just print the triangle!
  */
-    public char[][] generateTriangle(int n) {
+    public char[][] generateTriangle(int n)
+    {
+        if (n <= 0)
+            return new char[0][0];
 
-        // todo
+        char[][] triangle = new char[n][];
-        return null;
 
+        for (int row = 0; row < n; row++)
+        {
+            triangle[row] = new char[row + 1];
+
+            for (int col = 0; col < row + 1; col++)
+            {
+                if((row == col) || (row == n-1) || (col == 0))
+                    triangle[row][col] = '*';
+                else
+                    triangle[row][col] = ' ';
+            }
+        }
+
+        return triangle;
     }
 
 
 
+
+
     /*
        SPIRAL TRAVERSAL OF A RECTANGULAR MATRIX
 
@@ -57,11 +78,57 @@ public class MainExercises
            - Number of rows:    matrix.length
            - Number of columns: matrix[0].length (if rectangular)
    */
-    public int[] spiralTraversal(int[][] matrix) {
+    public int[] spiralTraversal(int[][] matrix)
-        // todo
+    {
-        return null;
+        if (matrix == null || matrix.length == 0 || matrix[0].length == 0)
+            return new int[0];
+
+        int rows = matrix.length;
+        int cols = matrix[0].length;
+
+        int[] result = new int[rows * cols];
+        int index = 0;
+
+        int top = 0, bottom = rows - 1;
+        int left = 0, right = cols - 1;
+
+        while (top <= bottom && left <= right)
+        {
+            // move right
+            for (int c = left; c <= right; c++)
+                result[index++] = matrix[top][c];
+
+            top++;
+
+            // move down
+            for (int r = top; r <= bottom; r++)
+                result[index++] = matrix[r][right];
+
+            right--;
+
+            if (top <= bottom)
+            {
+                // move left
+                for (int c = right; c >= left; c--)
+                    result[index++] = matrix[bottom][c];
+
+                bottom--;
+            }
+
+            if (left <= right)
+            {
+                // move up
+                for (int r = bottom; r >= top; r--)
+                    result[index++] = matrix[r][left];
+
+                left++;
+            }
+        }
+
+        return result;
     }
 
+
     /*
         integer partitioning is a combinatorics problem in discreet maths
         the problem is to generate sum numbers which their summation is the input number
@@ -90,11 +157,42 @@ public class MainExercises
         body to use them instead of arrays.
     */
 
-    public int[][] intPartitions(int n) {
+    public int[][] intPartitions(int n)
-        // todo
+    {
-        return null;
+        List<List<Integer>> result = new ArrayList<>();
+
+        generatePartitions(n, n, new ArrayList<>(), result);
+
+        int[][] arr = new int[result.size()][];
+
+        for (int i = 0; i < result.size(); i++)
+        {
+            List<Integer> part = result.get(i);
+            arr[i] = new int[part.size()];
+
+            for (int j = 0; j < part.size(); j++)
+                arr[i][j] = part.get(j);
+        }
+        return arr;
     }
 
+    private void generatePartitions(int remaining, int max, List<Integer> current, List<List<Integer>> result)
+    {
+        if (remaining == 0)
+        {
+            result.add(new ArrayList<>(current));
+            return;
+        }
+
+        for (int i = Math.min(max, remaining); i >= 1; i--)
+        {
+            current.add(i);
+            generatePartitions(remaining - i, i, current, result);
+            current.remove(current.size() - 1);
+        }
+    }
+
+
 
     public static void main()
     {