Add MaxAlternatingSum algorithm implementation

Refactored maxAlternatingSum method to use squared values and improved variable naming.

Author: Jashnavi25

src/main/java/com/thealgorithms/devutils/MaxAlternatingSum.java

@@ -1,19 +1,43 @@
-import java.util.*;
-class Solution {
+package com.thealgorithms.devutils;
+
+import java.util.Arrays;
+
+/**
+ * Computes the maximum alternating sum based on the squared values of the input array.
+ *
+ * Steps:
+ * 1. Convert nums[i] to nums[i]^2
+ * 2. Sort the squared array
+ * 3. Select the largest (n + 1) / 2 elements
+ * 4. Use formula: result = 2 * sum(selected) - totalSum
+ *
+ * Time Complexity: O(n log n)
+ * Space Complexity: O(n)
+ */
+public class MaxAlternatingSum {
+
     public long maxAlternatingSum(int[] nums) {
-        int n=nums.length;
-        long[] a=new long[n];
-        for(int i=0;i<n;i++){
-            a[i]=(long)nums[i]*nums[i];
+        int n = nums.length;
+        long[] squared = new long[n];
+
+        for (int i = 0; i < n; i++) {
+            squared[i] = (long) nums[i] * nums[i];
         }
-        Arrays.sort(a);
-        int k=(n+1)/2;
-        long total=0;
-        for(long v : a) total+=v;
-        long sum=0;
-        for(int i=n-1;i>=n-k;i--){
-            sum +=a[i];
+
+        Arrays.sort(squared);
+
+        int k = (n + 1) / 2;
+
+        long total = 0;
+        for (long v : squared) {
+            total += v;
         }
-        return 2*sum-total;
+
+        long maxHalf = 0;
+        for (int i = n - 1; i >= n - k; i--) {
+            maxHalf += squared[i];
+        }
+
+        return 2 * maxHalf - total;
     }
 }