Merge branch 'master' into refactor/DuplicateBrackets

Author: alxkm

src/main/java/com/thealgorithms/datastructures/lists/CircleLinkedList.java

@@ -51,22 +51,25 @@ public void append(E value) {
         size++;
     }
 
-    // utility function for traversing the list
     public String toString() {
-        Node<E> p = head.next;
-        String s = "[ ";
-        while (p != head) {
-            s += p.value;
-            if (p != tail) {
-                s += " , ";
+        if (size == 0) {
+            return "[]";
+        }
+        StringBuilder sb = new StringBuilder("[ ");
+        Node<E> current = head.next;
+        while (current != head) {
+            sb.append(current.value);
+            if (current.next != head) {
+                sb.append(", ");
             }
-            p = p.next;
+            current = current.next;
         }
-        return s + " ]";
+        sb.append(" ]");
+        return sb.toString();
     }
 
     public E remove(int pos) {
-        if (pos > size || pos < 0) {
+        if (pos >= size || pos < 0) {
             // catching errors
             throw new IndexOutOfBoundsException("position cannot be greater than size or negative");
         }
@@ -89,18 +92,4 @@ public E remove(int pos) {
         size--;
         return saved;
     }
-
-    public static void main(String[] args) {
-        CircleLinkedList<Integer> cl = new CircleLinkedList<>();
-        cl.append(12);
-        System.out.println(cl);
-        cl.append(23);
-        System.out.println(cl);
-        cl.append(34);
-        System.out.println(cl);
-        cl.append(56);
-        System.out.println(cl);
-        cl.remove(3);
-        System.out.println(cl);
-    }
 }

src/main/java/com/thealgorithms/dynamicprogramming/LongestPalindromicSubstring.java

@@ -1,25 +1,18 @@
 package com.thealgorithms.dynamicprogramming;
 
-/*
- * Algorithm explanation https://leetcode.com/problems/longest-palindromic-substring/
+/**
+ * Class for finding the longest palindromic substring within a given string.
+ * <p>
+ * A palindromic substring is a sequence of characters that reads the same backward as forward.
+ * This class uses a dynamic programming approach to efficiently find the longest palindromic substring.
+ *
  */
 public final class LongestPalindromicSubstring {
     private LongestPalindromicSubstring() {
     }
 
-    public static void main(String[] args) {
-        String a = "babad";
-        String b = "cbbd";
-
-        String aLPS = lps(a);
-        String bLPS = lps(b);
-
-        System.out.println(a + " => " + aLPS);
-        System.out.println(b + " => " + bLPS);
-    }
-
-    private static String lps(String input) {
-        if (input == null || input.length() == 0) {
+    public static String lps(String input) {
+        if (input == null || input.isEmpty()) {
             return input;
         }
         boolean[][] arr = new boolean[input.length()][input.length()];

src/main/java/com/thealgorithms/others/CountChar.java

@@ -5,13 +5,16 @@ private CountChar() {
     }
 
     /**
-     * Count non space character in string
+     * Counts the number of non-whitespace characters in the given string.
      *
-     * @param str String to count the characters
-     * @return number of character in the specified string
+     * @param str the input string to count the characters in
+     * @return the number of non-whitespace characters in the specified string;
+     *         returns 0 if the input string is null
      */
-
     public static int countCharacters(String str) {
+        if (str == null) {
+            return 0;
+        }
         return str.replaceAll("\\s", "").length();
     }
 }

src/main/java/com/thealgorithms/strings/LongestNonRepetitiveSubstring.java

@@ -3,47 +3,40 @@
 import java.util.HashMap;
 import java.util.Map;
 
+/**
+ * Class for finding the length of the longest substring without repeating characters.
+ */
 final class LongestNonRepetitiveSubstring {
     private LongestNonRepetitiveSubstring() {
     }
 
+    /**
+     * Finds the length of the longest substring without repeating characters.
+     *
+     * @param s the input string
+     * @return the length of the longest non-repetitive substring
+     */
     public static int lengthOfLongestSubstring(String s) {
-        int max = 0;
+        int maxLength = 0;
         int start = 0;
-        int i = 0;
-        Map<Character, Integer> map = new HashMap<>();
-
-        while (i < s.length()) {
-            char temp = s.charAt(i);
-
-            // adding key to map if not present
-            if (!map.containsKey(temp)) {
-                map.put(temp, 0);
-            } else if (s.charAt(start) == temp) {
-                start++;
-            } else if (s.charAt(i - 1) == temp) {
-                if (max < map.size()) {
-                    max = map.size();
-                }
-                map = new HashMap<>();
-                start = i;
-                i--;
-            } else {
-                if (max < map.size()) {
-                    max = map.size();
-                }
-                while (s.charAt(start) != temp) {
-                    map.remove(s.charAt(start));
-                    start++;
-                }
-                start++;
+        Map<Character, Integer> charIndexMap = new HashMap<>();
+
+        for (int i = 0; i < s.length(); i++) {
+            char currentChar = s.charAt(i);
+
+            // If the character is already in the map and its index is within the current window
+            if (charIndexMap.containsKey(currentChar) && charIndexMap.get(currentChar) >= start) {
+                // Move the start to the position right after the last occurrence of the current character
+                start = charIndexMap.get(currentChar) + 1;
             }
 
-            i++;
-        }
-        if (max < map.size()) {
-            max = map.size();
+            // Update the last seen index of the current character
+            charIndexMap.put(currentChar, i);
+
+            // Calculate the maximum length of the substring without repeating characters
+            maxLength = Math.max(maxLength, i - start + 1);
         }
-        return max;
+
+        return maxLength;
     }
 }

src/test/java/com/thealgorithms/datastructures/lists/CircleLinkedListTest.java

@@ -0,0 +1,78 @@
+package com.thealgorithms.datastructures.lists;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+import org.junit.jupiter.api.Test;
+
+public class CircleLinkedListTest {
+
+    @Test
+    public void testAppendAndSize() {
+        CircleLinkedList<Integer> list = new CircleLinkedList<>();
+        list.append(1);
+        list.append(2);
+        list.append(3);
+
+        assertEquals(3, list.getSize());
+        assertEquals("[ 1, 2, 3 ]", list.toString());
+    }
+
+    @Test
+    public void testRemove() {
+        CircleLinkedList<Integer> list = new CircleLinkedList<>();
+        list.append(1);
+        list.append(2);
+        list.append(3);
+        list.append(4);
+
+        assertEquals(2, list.remove(1));
+        assertEquals(3, list.remove(1));
+        assertEquals("[ 1, 4 ]", list.toString());
+        assertEquals(2, list.getSize());
+    }
+
+    @Test
+    public void testRemoveInvalidIndex() {
+        CircleLinkedList<Integer> list = new CircleLinkedList<>();
+        list.append(1);
+        list.append(2);
+
+        assertThrows(IndexOutOfBoundsException.class, () -> list.remove(2));
+        assertThrows(IndexOutOfBoundsException.class, () -> list.remove(-1));
+    }
+
+    @Test
+    public void testToStringEmpty() {
+        CircleLinkedList<Integer> list = new CircleLinkedList<>();
+        assertEquals("[]", list.toString());
+    }
+
+    @Test
+    public void testToStringAfterRemoval() {
+        CircleLinkedList<Integer> list = new CircleLinkedList<>();
+        list.append(1);
+        list.append(2);
+        list.append(3);
+        list.remove(1);
+
+        assertEquals("[ 1, 3 ]", list.toString());
+    }
+
+    @Test
+    public void testSingleElement() {
+        CircleLinkedList<Integer> list = new CircleLinkedList<>();
+        list.append(1);
+
+        assertEquals(1, list.getSize());
+        assertEquals("[ 1 ]", list.toString());
+        assertEquals(1, list.remove(0));
+        assertEquals("[]", list.toString());
+    }
+
+    @Test
+    public void testNullElement() {
+        CircleLinkedList<String> list = new CircleLinkedList<>();
+        assertThrows(NullPointerException.class, () -> list.append(null));
+    }
+}

src/test/java/com/thealgorithms/dynamicprogramming/LongestPalindromicSubstringTest.java

@@ -0,0 +1,22 @@
+package com.thealgorithms.dynamicprogramming;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import java.util.stream.Stream;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.Arguments;
+import org.junit.jupiter.params.provider.MethodSource;
+
+public class LongestPalindromicSubstringTest {
+
+    private static Stream<Arguments> provideTestCases() {
+        return Stream.of(
+            Arguments.of("babad", "aba"), Arguments.of("cbbd", "bb"), Arguments.of("a", "a"), Arguments.of("x", "x"), Arguments.of("", ""), Arguments.of("aaaa", "aaaa"), Arguments.of("mm", "mm"), Arguments.of("level", "level"), Arguments.of("bananas", "anana"), Arguments.of("abacabad", "abacaba"));
+    }
+
+    @ParameterizedTest
+    @MethodSource("provideTestCases")
+    public void testLps(String input, String expected) {
+        assertEquals(expected, LongestPalindromicSubstring.lps(input));
+    }
+}

src/test/java/com/thealgorithms/others/CountCharTest.java

@@ -2,15 +2,23 @@
 
 import static org.junit.jupiter.api.Assertions.assertEquals;
 
+import org.junit.jupiter.api.DisplayName;
 import org.junit.jupiter.api.Test;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.CsvSource;
 
 class CountCharTest {
 
-    @Test
-    void testCountCharacters() {
-        String input = "12345";
-        int expectedValue = 5;
+    @ParameterizedTest(name = "\"{0}\" should have {1} non-whitespace characters")
+    @CsvSource({"'', 0", "'   ', 0", "'a', 1", "'abc', 3", "'a b c', 3", "'   a   b   c   ', 3", "'\tabc\n', 3", "'  a   b\tc  ', 3", "' 12345 ', 5", "'Hello, World!', 12"})
+    @DisplayName("Test countCharacters with various inputs")
+    void testCountCharacters(String input, int expected) {
+        assertEquals(expected, CountChar.countCharacters(input));
+    }
 
-        assertEquals(expectedValue, CountChar.countCharacters(input));
+    @Test
+    @DisplayName("Test countCharacters with null input")
+    void testCountCharactersNullInput() {
+        assertEquals(0, CountChar.countCharacters(null));
     }
 }

src/test/java/com/thealgorithms/strings/LongestNonRepetitiveSubstringTest.java

@@ -1,15 +1,22 @@
 package com.thealgorithms.strings;
 
-import org.junit.jupiter.api.Assertions;
-import org.junit.jupiter.api.Test;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import java.util.stream.Stream;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.Arguments;
+import org.junit.jupiter.params.provider.MethodSource;
 
 public class LongestNonRepetitiveSubstringTest {
 
-    @Test
-    public void palindrome() {
-        String input1 = "HelloWorld";
-        String input2 = "javaIsAProgrammingLanguage";
-        Assertions.assertEquals(LongestNonRepetitiveSubstring.lengthOfLongestSubstring(input1), 5);
-        Assertions.assertEquals(LongestNonRepetitiveSubstring.lengthOfLongestSubstring(input2), 9);
+    private static Stream<Arguments> provideTestCases() {
+        return Stream.of(Arguments.of("", 0), Arguments.of("a", 1), Arguments.of("abcde", 5), Arguments.of("aaaaa", 1), Arguments.of("abca", 3), Arguments.of("abcdeabc", 5), Arguments.of("a1b2c3", 6), Arguments.of("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890", 62),
+            Arguments.of("aabb", 2), Arguments.of("abcdefghijabc", 10));
+    }
+
+    @ParameterizedTest
+    @MethodSource("provideTestCases")
+    void testLengthOfLongestSubstring(String input, int expectedLength) {
+        assertEquals(expectedLength, LongestNonRepetitiveSubstring.lengthOfLongestSubstring(input));
     }
 }