resolved issues

Author: Darshan-Baligeri

src/main/java/com/thealgorithms/shufflealogrithm/ConstrainedShuffle.java

@@ -3,9 +3,11 @@
 import java.util.Arrays;
 import java.util.Random;
 
-public final class ConstrainedShuffle {
+public
+final class ConstrainedShuffle {
 
-    private ConstrainedShuffle() {
+    private
+    ConstrainedShuffle() {
         // Prevent instantiation
     }
 
@@ -15,25 +17,29 @@ private ConstrainedShuffle() {
      *
      * @param array the input array to shuffle
      */
-    public static void constrainedShuffle(int[] array) {
+    public
+    static void constrainedShuffle(int[] array) {
         // Edge case: If the array has less than 3 elements, no shuffling can occur
         if (array == null || array.length < 3) {
             return;
         }
 
         Random random = new Random();
-        for (int i = array.length - 1; i > 1; i--) {
+        // Start loop from the second last element and exclude the first and last
+        // elements
+        for (int i = array.length - 2; i > 1; i--) {
             // Generate a random index between 1 and i (inclusive)
             int j = random.nextInt(i - 1) + 1;
 
             // Swap the elements at positions i and j
-            int temp = array[i]; // Temporarily store the element at i
-            array[i] = array[j]; // Move element from j to i
-            array[j] = temp;     // Place the stored element in position j
+            int temp = array[i];
+            array[i] = array[j];
+            array[j] = temp;
         }
     }
 
-    public static void main(String[] args) {
+    public
+    static void main(String[] args) {
         int[] array = {1, 2, 3, 4, 5};
         System.out.println("Original Array: " + Arrays.toString(array));
         constrainedShuffle(array);

src/main/java/com/thealgorithms/shufflealogrithm/GroupShuffle.java

@@ -4,9 +4,11 @@
 import java.util.Collections;
 import java.util.List;
 
-public final class GroupShuffle {
+public
+final class GroupShuffle {
 
-    private GroupShuffle() {
+    private
+    GroupShuffle() {
         // Prevent instantiation
     }
 
@@ -17,7 +19,8 @@ private GroupShuffle() {
      * @param groupSize the size of each group
      * @return a list of shuffled groups
      */
-    public static List<List<Integer>> groupShuffle(int[] array, int groupSize) {
+    public
+    static List<List<Integer>> groupShuffle(int[] array, int groupSize) {
         List<List<Integer>> groups = new ArrayList<>();
 
         // Edge case: Check if the group size is valid
@@ -33,12 +36,16 @@ public static List<List<Integer>> groupShuffle(int[] array, int groupSize) {
             groups.add(group);
         }
 
-        // Shuffle the groups to randomize their order
-        Collections.shuffle(groups);
+        // Shuffle only if the group size is greater than 1
+        if (groupSize > 1) {
+            Collections.shuffle(groups);
+        }
+
         return groups;
     }
 
-    public static void main(String[] args) {
+    public
+    static void main(String[] args) {
         int[] array = {1, 2, 3, 4, 5, 6, 7, 8, 9};
         List<List<Integer>> shuffledGroups = groupShuffle(array, 3);
 

src/main/java/com/thealgorithms/shufflealogrithm/WeightedShuffle.java

@@ -2,10 +2,13 @@
 
 import java.util.Arrays;
 import java.util.Comparator;
+import java.util.Random;
 
-public final class WeightedShuffle {
+public
+final class WeightedShuffle {
 
-    private WeightedShuffle() {
+    private
+    WeightedShuffle() {
         // Prevent instantiation
     }
 
@@ -16,7 +19,8 @@ private WeightedShuffle() {
      * @param array   the input array to shuffle
      * @param weights the weights for each corresponding element in the array
      */
-    public static void weightedShuffle(int[] array, int[] weights) {
+    public
+    static void weightedShuffle(int[] array, int[] weights) {
         // Edge case: Check if weights match the array size
         if (array == null || weights == null || array.length != weights.length) {
             return;
@@ -27,7 +31,12 @@ public static void weightedShuffle(int[] array, int[] weights) {
             indices[i] = i;
         }
 
-        Arrays.sort(indices, Comparator.comparingInt(i -> - weights[i]));
+        Random random = new Random();
+
+        // Sort indices by weights in descending order, with a random factor for
+        // ties
+        Arrays.sort(indices, Comparator.<Integer>comparingInt(i->- weights[i])
+                .thenComparingInt(i->random.nextInt()));
 
         int[] result = new int[array.length];
         for (int i = 0; i < array.length; i++) {
@@ -37,7 +46,8 @@ public static void weightedShuffle(int[] array, int[] weights) {
         System.arraycopy(result, 0, array, 0, array.length);
     }
 
-    public static void main(String[] args) {
+    public
+    static void main(String[] args) {
         int[] array = {10, 20, 30};
         int[] weights = {1, 3, 2};
         weightedShuffle(array, weights);