Refactor PowerSum algorithm implementation and documentation

Author: manishraj27

src/main/java/com/thealgorithms/backtracking/PowerSum.java

@@ -1,36 +1,28 @@
-package com.thealgorithms.backtracking;
-
-/**
- * Problem Statement:
- * Find the number of ways that a given integer, N, can be expressed as the sum of the Xth powers
- * of unique, natural numbers.
- * For example, if N=100 and X=3, we have to find all combinations of unique cubes adding up to 100.
- * The only solution is 1^3 + 2^3 + 3^3 + 4^3. Therefore, the output will be 1.
- *
- * N is represented by the parameter 'targetSum' in the code.
- * X is represented by the parameter 'power' in the code.
- */
 public class PowerSum {
 
     /**
      * Calculates the number of ways to express the target sum as a sum of Xth powers of unique natural numbers.
      *
-     * targetSum The target sum to achieve (N in the problem statement)
-     * power The power to raise natural numbers to (X in the problem statement)
-     *  The number of ways to express the target sum
+     * @param targetSum The target sum to achieve (N in the problem statement)
+     * @param power The power to raise natural numbers to (X in the problem statement)
+     * @return The number of ways to express the target sum
      */
     public int powSum(int targetSum, int power) {
+        // Special case: when both targetSum and power are zero
+        if (targetSum == 0 && power == 0) {
+            return 1; // by convention, one way to sum to zero: use nothing
+        }
         return sumRecursive(targetSum, power, 1, 0);
     }
 
     /**
      * Recursively calculates the number of ways to express the remaining sum as a sum of Xth powers.
      *
-     * remainingSum The remaining sum to achieve
-     * power The power to raise natural numbers to (X in the problem statement)
-     * currentNumber The current natural number being considered
-     * currentSum The current sum of powered numbers
-     * The number of valid combinations
+     * @param remainingSum The remaining sum to achieve
+     * @param power The power to raise natural numbers to (X in the problem statement)
+     * @param currentNumber The current natural number being considered
+     * @param currentSum The current sum of powered numbers
+     * @return The number of valid combinations
      */
     private int sumRecursive(int remainingSum, int power, int currentNumber, int currentSum) {
         int newSum = currentSum + (int) Math.pow(currentNumber, power);