Merge pull request #182 from ApsaraGuhan/dynamicprogramming_knapsack

Adding implementation of knapsack

dynamic_programming/knapsack.rb

@@ -0,0 +1,64 @@
+require "test/unit"
+
+# 0-1 Knapsack problem
+# The function returns the maximum value that can be put in a knapsack of a given capacity
+ 
+def knapSack(weight, wt, val, n)
+    
+    rows, cols = n+1,weight+1  
+    # Create a 2D array to store results of subproblems
+    dp = Array.new(rows) { Array.new(cols) }
+    
+    for i in (0..n + 1-1) 
+        for w in (0..weight + 1-1) 
+            # if the weight is 0 or value is zero, the corresponding cell in the 2D array is set to 0
+            if i == 0 || w == 0 
+                dp[i][w] = 0
+            
+            #If the weight of an element is less than the capacity of the bag, the maximum value of the two cases is taken(Either the element is taken into consideration
+            #or is ignored)
+            elsif wt[i-1] <= w 
+                dp[i][w] = [ val[i-1] + dp[i-1][w-wt[i-1]],dp[i-1][w]].max()
+           
+            #If the weight of the element is greater than the capacity of the bag, the cell is set to the value of the previous cell
+            else
+                dp[i][w] = dp[i-1][w]
+            end
+        end
+    end
+    
+    return dp[n][weight]
+end
+    
+  
+
+
+
+class Knapsacktest < Test::Unit::TestCase
+    
+    #Test1
+    def test_knapsack1
+      assert_equal 220, knapSack(50,[10,20,30],[60,100,120],3), "Should return 220" 
+    end
+
+
+    #Test2
+    def test_knapsack2
+      assert_equal 500, knapSack(50,[50, 20, 30],[100, 200, 300],3), "Should return 500" 
+    end
+
+    #Test3
+    def test_knapsack3
+        assert_equal 17, knapSack(10,[3,4,5, 2, 1],[10,2,3,4,0],5), "Should return 17" 
+    end
+
+    #Test4
+    def test_knapsack4
+        assert_equal 0, knapSack(0,[23, 17, 12, 8, 20],[199,200,30,41,10],5), "Should return 0" 
+    end
+
+
+end
+
+
+