diff --git a/DIRECTORY.md b/DIRECTORY.md index fb5ff2fed57b..1e5210730b4d 100644 --- a/DIRECTORY.md +++ b/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 diff --git a/src/main/java/com/thealgorithms/dynamicprogramming/WineProblem.java b/src/main/java/com/thealgorithms/dynamicprogramming/WineProblem.java index 0f5359f4d95e..022b43184a88 100644 --- a/src/main/java/com/thealgorithms/dynamicprogramming/WineProblem.java +++ b/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/ diff --git a/src/test/java/com/thealgorithms/dynamicprogramming/WineProblemTest.java b/src/test/java/com/thealgorithms/dynamicprogramming/WineProblemTest.java new file mode 100644 index 000000000000..fbcc2c6f3a83 --- /dev/null +++ b/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."); + } +}