Add MaxAlternatingSum algorithm implementation

Author: Jashnavi25

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

@@ -0,0 +1,19 @@
+import java.util.*;
+class Solution {
+    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];
+        }
+        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];
+        }
+        return 2*sum-total;
+    }
+}