From 16e764c942b08449701a7b24521570ea1188bd11 Mon Sep 17 00:00:00 2001
From: Gang <Wu>
Date: Mon, 14 Oct 2019 14:48:50 -0600
Subject: [PATCH 1/2] BAEL-3349 Knapsack problem implementation in Java

---
 .../algorithms/knapsack/Knapsack.java         | 32 ++++++++++++++
 .../algorithms/knapsack/KnapsackUnitTest.java | 44 +++++++++++++++++++
 2 files changed, 76 insertions(+)
 create mode 100644 algorithms-miscellaneous-5/src/main/java/com/baeldung/algorithms/knapsack/Knapsack.java
 create mode 100644 algorithms-miscellaneous-5/src/test/java/com/baeldung/algorithms/knapsack/KnapsackUnitTest.java

diff --git a/algorithms-miscellaneous-5/src/main/java/com/baeldung/algorithms/knapsack/Knapsack.java b/algorithms-miscellaneous-5/src/main/java/com/baeldung/algorithms/knapsack/Knapsack.java
new file mode 100644
index 0000000000..a53ab21429
--- /dev/null
+++ b/algorithms-miscellaneous-5/src/main/java/com/baeldung/algorithms/knapsack/Knapsack.java
@@ -0,0 +1,32 @@
+package com.baeldung.algorithms.knapsack;
+
+class Knapsack {
+
+    public int knapsackRec(int[] w, int[] v, int n, int W) {
+        if (n <= 0)
+            return 0;
+        else if (w[n - 1] > W)
+            return knapsackRec(w, v, n - 1, W);
+        else
+            return Math.max(knapsackRec(w, v, n - 1, W), v[n - 1] + knapsackRec(w, v, n - 1, W - w[n - 1]));
+    }
+
+    public int knapsackDP(int[] w, int[] v, int n, int W) {
+        if (n <= 0 || W <= 0)
+            return 0;
+        int[][] m = new int[n + 1][W + 1];
+        for (int j = 0; j <= W; j++) {
+            m[0][j] = 0;
+        }
+
+        for (int i = 1; i <= n; i++) {
+            for (int j = 1; j <= W; j++) {
+                if (w[i - 1] > j)
+                    m[i][j] = m[i - 1][j];
+                else
+                    m[i][j] = Math.max(m[i - 1][j], m[i - 1][j - w[i - 1]] + v[i - 1]);
+            }
+        }
+        return m[n][W];
+    }
+}
diff --git a/algorithms-miscellaneous-5/src/test/java/com/baeldung/algorithms/knapsack/KnapsackUnitTest.java b/algorithms-miscellaneous-5/src/test/java/com/baeldung/algorithms/knapsack/KnapsackUnitTest.java
new file mode 100644
index 0000000000..b168e6b1eb
--- /dev/null
+++ b/algorithms-miscellaneous-5/src/test/java/com/baeldung/algorithms/knapsack/KnapsackUnitTest.java
@@ -0,0 +1,44 @@
+package com.baeldung.algorithms.knapsack;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import org.junit.jupiter.api.Test;
+
+public class KnapsackUnitTest {
+
+    @Test
+    public void givenWeightsandValues_whenCalculateMax_thenOutputCorrectResult() {
+        final int[] w = new int[] { 23, 26, 20, 18, 32, 27, 29, 26, 30, 27 };
+        final int[] v = new int[] { 505, 352, 458, 220, 354, 414, 498, 545, 473, 543 };
+        final int n = 10;
+        final int W = 67;
+        final Knapsack knapsack = new Knapsack();
+
+        assertEquals(1270, knapsack.knapsackRec(w, v, n, W));
+        assertEquals(1270, knapsack.knapsackDP(w, v, n, W));
+    }
+
+    @Test
+    public void givenZeroItems_whenCalculateMax_thenOutputZero() {
+        final int[] w = new int[] {};
+        final int[] v = new int[] {};
+        final int n = 0;
+        final int W = 67;
+        final Knapsack knapsack = new Knapsack();
+
+        assertEquals(0, knapsack.knapsackRec(w, v, n, W));
+        assertEquals(0, knapsack.knapsackDP(w, v, n, W));
+    }
+
+    @Test
+    public void givenZeroWeightLimit_whenCalculateMax_thenOutputZero() {
+        final int[] w = new int[] { 23, 26, 20, 18, 32, 27, 29, 26, 30, 27 };
+        final int[] v = new int[] { 505, 352, 458, 220, 354, 414, 498, 545, 473, 543 };
+        final int n = 10;
+        final int W = 0;
+        final Knapsack knapsack = new Knapsack();
+
+        assertEquals(0, knapsack.knapsackRec(w, v, n, W));
+        assertEquals(0, knapsack.knapsackDP(w, v, n, W));
+    }
+}

From 85b5042cb7c6ca1c7c09dcfa7f782cc66648376e Mon Sep 17 00:00:00 2001
From: Gang <Wu>
Date: Tue, 15 Oct 2019 21:19:57 -0600
Subject: [PATCH 2/2] BAEL-3349, Add brackets and make the class public

---
 .../baeldung/algorithms/knapsack/Knapsack.java | 18 +++++++++++-------
 1 file changed, 11 insertions(+), 7 deletions(-)

diff --git a/algorithms-miscellaneous-5/src/main/java/com/baeldung/algorithms/knapsack/Knapsack.java b/algorithms-miscellaneous-5/src/main/java/com/baeldung/algorithms/knapsack/Knapsack.java
index a53ab21429..61c3f05a95 100644
--- a/algorithms-miscellaneous-5/src/main/java/com/baeldung/algorithms/knapsack/Knapsack.java
+++ b/algorithms-miscellaneous-5/src/main/java/com/baeldung/algorithms/knapsack/Knapsack.java
@@ -1,19 +1,22 @@
 package com.baeldung.algorithms.knapsack;
 
-class Knapsack {
+public class Knapsack {
 
     public int knapsackRec(int[] w, int[] v, int n, int W) {
-        if (n <= 0)
+        if (n <= 0) {
             return 0;
-        else if (w[n - 1] > W)
+        } else if (w[n - 1] > W) {
             return knapsackRec(w, v, n - 1, W);
-        else
+        } else {
             return Math.max(knapsackRec(w, v, n - 1, W), v[n - 1] + knapsackRec(w, v, n - 1, W - w[n - 1]));
+        }
     }
 
     public int knapsackDP(int[] w, int[] v, int n, int W) {
-        if (n <= 0 || W <= 0)
+        if (n <= 0 || W <= 0) {
             return 0;
+        }
+
         int[][] m = new int[n + 1][W + 1];
         for (int j = 0; j <= W; j++) {
             m[0][j] = 0;
@@ -21,10 +24,11 @@ class Knapsack {
 
         for (int i = 1; i <= n; i++) {
             for (int j = 1; j <= W; j++) {
-                if (w[i - 1] > j)
+                if (w[i - 1] > j) {
                     m[i][j] = m[i - 1][j];
-                else
+                } else {
                     m[i][j] = Math.max(m[i - 1][j], m[i - 1][j - w[i - 1]] + v[i - 1]);
+                }
             }
         }
         return m[n][W];