June 2018 Update

Task/Knapsack-problem-Continuous/Julia/knapsack-problem-continuous-1.julia

@@ -1,29 +1,30 @@
-immutable KPCSupply{S<:String, T<:Real}
-    item::S
+struct KPCSupply{T<:Real}
+    item::String
     weight::T
     value::T
     uvalue::T
 end
-Base.isless(a::KPCSupply, b::KPCSupply) = a.uvalue<b.uvalue
-
-function KPCSupply{S<:String, T<:Real}(item::S, weight::T, value::T)
-    KPCSupply(item, weight, value, value/weight)
+function KPCSupply(item::AbstractString, weight::Real, value::Real)
+    w, v = promote(weight, value)
+    KPCSupply(item, w, v, v / w)
 end
 
-function solve{S<:String, T<:Real}(store::Array{KPCSupply{S,T},1},
-                                   capacity::T)
-    ksack = KPCSupply{S,T}[]
+Base.show(io::IO, s::KPCSupply) = print(io, s.item, @sprintf " (%.2f kg, %.2f €, %.2f €/kg)" s.weight s.value s.uvalue)
+Base.isless(a::KPCSupply, b::KPCSupply) = a.uvalue < b.uvalue
+
+function solve(store::Vector{KPCSupply{T}}, capacity::Real) where T<:Real
+    sack = similar(store, 0) # vector like store, but of length 0
     kweight = zero(T)
-    for s in sort(store, rev=true)
-        if kweight + s.weight <= capacity
+    for s in sort(store, rev = true)
+        if kweight + s.weight ≤ capacity
             kweight += s.weight
-            push!(ksack, s)
+            push!(sack, s)
         else
-            w = capacity-kweight
-            v = w*s.uvalue
-            push!(ksack, KPCSupply(s.item, w, v, s.uvalue))
+            w = capacity - kweight
+            v = w * s.uvalue
+            push!(sack, KPCSupply(s.item, w, v, s.value))
             break
         end
     end
-    return ksack
+    return sack
 end

Task/Knapsack-problem-Continuous/Julia/knapsack-problem-continuous-2.julia

@@ -1,30 +1,14 @@
-store = [KPCSupply("beef", 38//10, 36//1),
-         KPCSupply("pork", 54//10, 43//1),
-         KPCSupply("ham", 36//10, 90//1),
-         KPCSupply("greaves", 24//10, 45//1),
-         KPCSupply("flitch", 4//1, 30//1),
-         KPCSupply("brawn", 25//10, 56//1),
-         KPCSupply("welt", 37//10, 67//1),
-         KPCSupply("salami", 3//1, 95//1),
-         KPCSupply("sausage", 59//10, 98//1)]
+store = [KPCSupply("beef", 38//10, 36),
+         KPCSupply("pork", 54//10, 43),
+         KPCSupply("ham", 36//10, 90),
+         KPCSupply("greaves", 24//10, 45),
+         KPCSupply("flitch", 4//1, 30),
+         KPCSupply("brawn", 25//10, 56),
+         KPCSupply("welt", 37//10, 67),
+         KPCSupply("salami", 3//1, 95),
+         KPCSupply("sausage", 59//10, 98)]
 
-sack = solve(store, 15//1)
-
-println("The store contains:")
-println("        Item Weight  Unit Price")
-for s in store
-    println(@sprintf("%12s %4.1f    %6.2f",
-                     s.item, float(s.weight), float(s.uvalue)))
-end
-
-println()
-println("The thief should take:")
-println("        Item Weight  Value")
-for s in sack
-    println(@sprintf("%12s %4.1f    %6.2f",
-                     s.item, float(s.weight), float(s.value)))
-end
-w = mapreduce(x->x.weight, +, sack)
-v = mapreduce(x->x.value, +, sack)
-println(@sprintf("%12s %4.1f    %6.2f",
-                 "Total", float(w), float(v)))
+sack = solve(store, 15)
+println("The store contains:\n - ", join(store, "\n - "))
+println("\nThe thief should take::\n - ", join(sack, "\n - "))
+@printf("\nTotal value in the sack: %.2f €\n", sum(getfield.(sack, :value)))