Add tests, add IllegalArgumentException, remove main in `WineProb… (#5662)

Author: Hardvan

DIRECTORY.md

@@ -833,6 +833,7 @@
             * [UniquePathsTests](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/dynamicprogramming/UniquePathsTests.java)
             * [UniqueSubsequencesCountTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/dynamicprogramming/UniqueSubsequencesCountTest.java)
             * [WildcardMatchingTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/dynamicprogramming/WildcardMatchingTest.java)
+            * [WineProblemTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/dynamicprogramming/WineProblemTest.java)
           * geometry
             * [GrahamScanTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/geometry/GrahamScanTest.java)
           * greedyalgorithms

src/main/java/com/thealgorithms/dynamicprogramming/WineProblem.java

@@ -1,21 +1,40 @@
 package com.thealgorithms.dynamicprogramming;
 
 /**
- * Imagine you have a collection of N wines placed next to each other on the
- * shelf. The price of ith wine is pi(Prices of different wines are different).
- * Because wine gets better every year supposing today is year 1, on year y the
- * price would be y*pi i.e y times the value of the initial year. You want to
- * sell all wines but you have to sell one wine per year. One more constraint on
- * each year you are allowed to sell either leftmost or rightmost wine on the
- * shelf. You are not allowed to reorder. You have to find the maximum profit
+ * The WineProblem class provides a solution to the wine selling problem.
+ * Given a collection of N wines with different prices, the objective is to maximize profit by selling
+ * one wine each year, considering the constraint that only the leftmost or rightmost wine can be sold
+ * at any given time.
  *
+ * The price of the ith wine is pi, and the selling price increases by a factor of the year in which
+ * it is sold. This class implements three approaches to solve the problem:
+ *
+ * 1. **Recursion**: A straightforward recursive method that computes the maximum profit.
+ *    - Time Complexity: O(2^N)
+ *    - Space Complexity: O(N) due to recursive calls.
+ *
+ * 2. **Top-Down Dynamic Programming (Memoization)**: This approach caches the results of subproblems
+ *    to avoid redundant computations.
+ *    - Time Complexity: O(N^2)
+ *    - Space Complexity: O(N^2) for the storage of results and O(N) for recursion stack.
+ *
+ * 3. **Bottom-Up Dynamic Programming (Tabulation)**: This method builds a table iteratively to
+ *    compute the maximum profit for all possible subproblems.
+ *    - Time Complexity: O(N^2)
+ *    - Space Complexity: O(N^2) for the table.
  */
 public final class WineProblem {
     private WineProblem() {
     }
 
-    // Method 1: Using Recursion
-    // Time Complexity=0(2^N) Space Complexity=Recursion extra space
+    /**
+     * Calculate maximum profit using recursion.
+     *
+     * @param arr Array of wine prices.
+     * @param si  Start index of the wine to consider.
+     * @param ei  End index of the wine to consider.
+     * @return Maximum profit obtainable by selling the wines.
+     */
     public static int wpRecursion(int[] arr, int si, int ei) {
         int n = arr.length;
         int year = (n - (ei - si + 1)) + 1;
@@ -29,8 +48,15 @@ public static int wpRecursion(int[] arr, int si, int ei) {
         return Math.max(start, end);
     }
 
-    // Method 2: Top-Down DP(Memoization)
-    // Time Complexity=0(N*N) Space Complexity=0(N*N)+Recursion extra space
+    /**
+     * Calculate maximum profit using top-down dynamic programming with memoization.
+     *
+     * @param arr  Array of wine prices.
+     * @param si   Start index of the wine to consider.
+     * @param ei   End index of the wine to consider.
+     * @param strg 2D array to store results of subproblems.
+     * @return Maximum profit obtainable by selling the wines.
+     */
     public static int wptd(int[] arr, int si, int ei, int[][] strg) {
         int n = arr.length;
         int year = (n - (ei - si + 1)) + 1;
@@ -45,15 +71,22 @@ public static int wptd(int[] arr, int si, int ei, int[][] strg) {
         int end = wptd(arr, si, ei - 1, strg) + arr[ei] * year;
 
         int ans = Math.max(start, end);
-
         strg[si][ei] = ans;
 
         return ans;
     }
 
-    // Method 3: Bottom-Up DP(Tabulation)
-    // Time Complexity=0(N*N/2)->0(N*N) Space Complexity=0(N*N)
+    /**
+     * Calculate maximum profit using bottom-up dynamic programming with tabulation.
+     *
+     * @param arr Array of wine prices.
+     * @throws IllegalArgumentException if the input array is null or empty.
+     * @return Maximum profit obtainable by selling the wines.
+     */
     public static int wpbu(int[] arr) {
+        if (arr == null || arr.length == 0) {
+            throw new IllegalArgumentException("Input array cannot be null or empty.");
+        }
         int n = arr.length;
         int[][] strg = new int[n][n];
 
@@ -73,13 +106,4 @@ public static int wpbu(int[] arr) {
         }
         return strg[0][n - 1];
     }
-
-    public static void main(String[] args) {
-        int[] arr = {2, 3, 5, 1, 4};
-        System.out.println("Method 1: " + wpRecursion(arr, 0, arr.length - 1));
-        System.out.println("Method 2: " + wptd(arr, 0, arr.length - 1, new int[arr.length][arr.length]));
-        System.out.println("Method 3: " + wpbu(arr));
-    }
 }
-// Memoization vs Tabulation : https://www.geeksforgeeks.org/tabulation-vs-memoization/
-// Question Link : https://www.geeksforgeeks.org/maximum-profit-sale-wines/

src/test/java/com/thealgorithms/dynamicprogramming/WineProblemTest.java

@@ -0,0 +1,72 @@
+package com.thealgorithms.dynamicprogramming;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+import org.junit.jupiter.api.Test;
+
+/**
+ * Unit tests for the WineProblem class.
+ * This test class verifies the correctness of the wine selling problem solutions.
+ */
+class WineProblemTest {
+
+    /**
+     * Test for wpRecursion method.
+     */
+    @Test
+    void testWpRecursion() {
+        int[] wines = {2, 3, 5, 1, 4}; // Prices of wines
+        int expectedProfit = 50; // The expected maximum profit
+        assertEquals(expectedProfit, WineProblem.wpRecursion(wines, 0, wines.length - 1), "The maximum profit using recursion should be 50.");
+    }
+
+    /**
+     * Test for wptd method (Top-Down DP with Memoization).
+     */
+    @Test
+    void testWptd() {
+        int[] wines = {2, 3, 5, 1, 4}; // Prices of wines
+        int expectedProfit = 50; // The expected maximum profit
+        assertEquals(expectedProfit, WineProblem.wptd(wines, 0, wines.length - 1, new int[wines.length][wines.length]), "The maximum profit using top-down DP should be 50.");
+    }
+
+    /**
+     * Test for wpbu method (Bottom-Up DP with Tabulation).
+     */
+    @Test
+    void testWpbu() {
+        int[] wines = {2, 3, 5, 1, 4}; // Prices of wines
+        int expectedProfit = 50; // The expected maximum profit
+        assertEquals(expectedProfit, WineProblem.wpbu(wines), "The maximum profit using bottom-up DP should be 50.");
+    }
+
+    /**
+     * Test with a single wine.
+     */
+    @Test
+    void testSingleWine() {
+        int[] wines = {10}; // Only one wine
+        int expectedProfit = 10; // Selling the only wine at year 1
+        assertEquals(expectedProfit, WineProblem.wpbu(wines), "The maximum profit for a single wine should be 10.");
+    }
+
+    /**
+     * Test with multiple wines of the same price.
+     */
+    @Test
+    void testSamePriceWines() {
+        int[] wines = {5, 5, 5}; // All wines have the same price
+        int expectedProfit = 30; // Profit is 5 * (1 + 2 + 3)
+        assertEquals(expectedProfit, WineProblem.wpbu(wines), "The maximum profit with same price wines should be 30.");
+    }
+
+    /**
+     * Test with no wines.
+     */
+    @Test
+    void testNoWines() {
+        int[] wines = {};
+        assertThrows(IllegalArgumentException.class, () -> WineProblem.wpbu(wines), "The maximum profit for no wines should throw an IllegalArgumentException.");
+    }
+}