cleanup: Improve docs, safety, and readability in RangeInSortedArray

src/main/java/com/thealgorithms/misc/RangeInSortedArray.java

@@ -1,25 +1,46 @@
 package com.thealgorithms.misc;
 
+/**
+ * Utility class for operations to find the range of occurrences of a key
+ * in a sorted (non-decreasing) array, and to count elements less than or equal to a given key.
+ */
 public final class RangeInSortedArray {
+
     private RangeInSortedArray() {
     }
 
-    // Get the 1st and last occurrence index of a number 'key' in a non-decreasing array 'nums'
-    // Gives [-1, -1] in case element doesn't exist in array
+    /**
+     * Finds the first and last occurrence indices of the key in a sorted array.
+     *
+     * @param nums sorted array of integers (non-decreasing order)
+     * @param key the target value to search for
+     * @return int array of size two where
+     *         - index 0 is the first occurrence of key,
+     *         - index 1 is the last occurrence of key,
+     *         or [-1, -1] if the key does not exist in the array.
+     */
     public static int[] sortedRange(int[] nums, int key) {
         int[] range = new int[] {-1, -1};
-        alteredBinSearchIter(nums, key, 0, nums.length - 1, range, true);
-        alteredBinSearchIter(nums, key, 0, nums.length - 1, range, false);
+        alteredBinSearchIter(nums, key, 0, nums.length - 1, range, true); // find left boundary
+        alteredBinSearchIter(nums, key, 0, nums.length - 1, range, false); // find right boundary
         return range;
     }
 
-    // Recursive altered binary search which searches for leftmost as well as rightmost occurrence
-    // of 'key'
+    /**
+     * Recursive altered binary search to find either the leftmost or rightmost occurrence of a key.
+     *
+     * @param nums the sorted array
+     * @param key the target to find
+     * @param left current left bound in search
+     * @param right current right bound in search
+     * @param range array to update with boundaries: range[0] for leftmost, range[1] for rightmost
+     * @param goLeft if true, searches for leftmost occurrence; if false, for rightmost occurrence
+     */
     public static void alteredBinSearch(int[] nums, int key, int left, int right, int[] range, boolean goLeft) {
         if (left > right) {
             return;
         }
-        int mid = (left + right) >>> 1;
+        int mid = left + ((right - left) >>> 1);
         if (nums[mid] > key) {
             alteredBinSearch(nums, key, left, mid - 1, range, goLeft);
         } else if (nums[mid] < key) {
@@ -41,11 +62,19 @@ public static void alteredBinSearch(int[] nums, int key, int left, int right, in
         }
     }
 
-    // Iterative altered binary search which searches for leftmost as well as rightmost occurrence
-    // of 'key'
+    /**
+     * Iterative altered binary search to find either the leftmost or rightmost occurrence of a key.
+     *
+     * @param nums the sorted array
+     * @param key the target to find
+     * @param left initial left bound
+     * @param right initial right bound
+     * @param range array to update with boundaries: range[0] for leftmost, range[1] for rightmost
+     * @param goLeft if true, searches for leftmost occurrence; if false, for rightmost occurrence
+     */
     public static void alteredBinSearchIter(int[] nums, int key, int left, int right, int[] range, boolean goLeft) {
         while (left <= right) {
-            final int mid = (left + right) >>> 1;
+            int mid = left + ((right - left) >>> 1);
             if (nums[mid] > key) {
                 right = mid - 1;
             } else if (nums[mid] < key) {
@@ -55,33 +84,48 @@ public static void alteredBinSearchIter(int[] nums, int key, int left, int right
                     if (mid == 0 || nums[mid - 1] != key) {
                         range[0] = mid;
                         return;
-                    } else {
-                        right = mid - 1;
                     }
+                    right = mid - 1;
                 } else {
                     if (mid == nums.length - 1 || nums[mid + 1] != key) {
                         range[1] = mid;
                         return;
-                    } else {
-                        left = mid + 1;
                     }
+                    left = mid + 1;
                 }
             }
         }
     }
 
+    /**
+     * Counts the number of elements strictly less than the given key.
+     *
+     * @param nums sorted array
+     * @param key the key to compare
+     * @return the count of elements less than the key
+     */
     public static int getCountLessThan(int[] nums, int key) {
         return getLessThan(nums, key, 0, nums.length - 1);
     }
 
+    /**
+     * Helper method using binary search to count elements less than or equal to the key.
+     *
+     * @param nums sorted array
+     * @param key the key to compare
+     * @param left current left bound
+     * @param right current right bound
+     * @return count of elements less than or equal to the key
+     */
     public static int getLessThan(int[] nums, int key, int left, int right) {
         int count = 0;
         while (left <= right) {
-            final int mid = (left + right) >>> 1;
+            int mid = left + ((right - left) >>> 1);
             if (nums[mid] > key) {
                 right = mid - 1;
-            } else if (nums[mid] <= key) {
-                count = mid + 1; // At least mid+1 elements exist which are <= key
+            } else {
+                // nums[mid] <= key
+                count = mid + 1; // all elements from 0 to mid inclusive are <= key
                 left = mid + 1;
             }
         }