Added Sum of Squares Lagrange's Four Square algorithm implementation (#6583)

* Add Sum of Squares algorithm implementation

* Format code and add Wikipedia URL for Lagrange's theorem

* Fixed clang-format issues

---------

Co-authored-by: Oleksandr Klymenko <alexanderklmn@gmail.com>

src/main/java/com/thealgorithms/maths/SumOfSquares.java

@@ -0,0 +1,53 @@
+package com.thealgorithms.maths;
+
+/**
+ * Implementation of Lagrange's Four Square Theorem
+ * Find minimum number of perfect squares that sum to given number
+ *
+ * @see <a href="https://en.wikipedia.org/wiki/Lagrange%27s_four-square_theorem">Lagrange's Four Square Theorem</a>
+ * @author BEASTSHRIRAM
+ */
+public final class SumOfSquares {
+
+    private SumOfSquares() {
+        // Utility class
+    }
+
+    /**
+     * Find minimum number of perfect squares that sum to n
+     *
+     * @param n the target number
+     * @return minimum number of squares needed
+     */
+    public static int minSquares(int n) {
+        if (isPerfectSquare(n)) {
+            return 1;
+        }
+
+        for (int i = 1; i * i <= n; i++) {
+            int remaining = n - i * i;
+            if (isPerfectSquare(remaining)) {
+                return 2;
+            }
+        }
+
+        // Legendre's three-square theorem
+        int temp = n;
+        while (temp % 4 == 0) {
+            temp /= 4;
+        }
+        if (temp % 8 == 7) {
+            return 4;
+        }
+
+        return 3;
+    }
+
+    private static boolean isPerfectSquare(int n) {
+        if (n < 0) {
+            return false;
+        }
+        int root = (int) Math.sqrt(n);
+        return root * root == n;
+    }
+}