Main

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

@@ -1,5 +1,7 @@
 package com.thealgorithms.dynamicprogramming;
 
+import java.util.Arrays;
+
 /**
  * Recursive Solution for 0-1 knapsack with memoization
  * This method is basically an extension to the recursive approach so that we
@@ -15,10 +17,8 @@ int knapSack(int capacity, int[] weights, int[] profits, int numOfItems) {
         int[][] dpTable = new int[numOfItems + 1][capacity + 1];
 
         // Loop to initially fill the table with -1
-        for (int i = 0; i < numOfItems + 1; i++) {
-            for (int j = 0; j < capacity + 1; j++) {
-                dpTable[i][j] = -1;
-            }
+        for (int[] table : dpTable) {
+            Arrays.fill(table, -1);
         }
 
         return solveKnapsackRecursive(capacity, weights, profits, numOfItems, dpTable);
@@ -38,7 +38,6 @@ int solveKnapsackRecursive(int capacity, int[] weights, int[] profits, int numOf
         if (weights[numOfItems - 1] > capacity) {
             // Store the value of function call stack in table
             dpTable[numOfItems][capacity] = solveKnapsackRecursive(capacity, weights, profits, numOfItems - 1, dpTable);
-            return dpTable[numOfItems][capacity];
         } else {
             // case 1. include the item, if it is less than the capacity
             final int includeCurrentItem = profits[numOfItems - 1] + solveKnapsackRecursive(capacity - weights[numOfItems - 1], weights, profits, numOfItems - 1, dpTable);
@@ -48,7 +47,7 @@ int solveKnapsackRecursive(int capacity, int[] weights, int[] profits, int numOf
 
             // Store the value of function call stack in table and return
             dpTable[numOfItems][capacity] = Math.max(includeCurrentItem, excludeCurrentItem);
-            return dpTable[numOfItems][capacity];
         }
+        return dpTable[numOfItems][capacity];
     }
 }

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

@@ -22,6 +22,10 @@ public static int cutRod(int[] price, int n) {
         if (price == null || price.length == 0) {
             throw new IllegalArgumentException("Price array cannot be null or empty.");
         }
+        // If rod length is negative
+        if (n < 0) {
+            throw new IllegalArgumentException("Rod length cannot be negative.");
+        }
         // Create an array to store the maximum obtainable values for each rod length.
         int[] val = new int[n + 1];
         val[0] = 0;

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

@@ -31,4 +31,19 @@ void test3() {
         int capacity = 50;
         assertEquals(220, knapsackMemoization.knapSack(capacity, weight, value, weight.length));
     }
+
+    @Test
+    void test4() {
+        int[] weight = {1, 2, 3};
+        int[] value = {10, 20, 30};
+        int capacity = 0;
+        assertEquals(0, knapsackMemoization.knapSack(capacity, weight, value, weight.length));
+    }
+    @Test
+    void test5() {
+        int[] weight = {1, 2, 3, 8};
+        int[] value = {10, 20, 30, 40};
+        int capacity = 50;
+        assertEquals(100, knapsackMemoization.knapSack(capacity, weight, value, weight.length));
+    }
 }

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

@@ -93,4 +93,10 @@ void testCutRodEmptyPrices() {
         int length = 5;
         assertThrows(IllegalArgumentException.class, () -> RodCutting.cutRod(prices, length), "An empty prices array should throw an IllegalArgumentException.");
     }
+    @Test
+    void testCutRodNegativeLength() {
+        int[] prices = {1, 5, 8, 9, 10};
+        int length = -1;
+        assertThrows(IllegalArgumentException.class, () -> RodCutting.cutRod(prices, length), "A negative rod length should throw an IllegalArgumentException.");
+    }
 }