Add exercise: anagram (JuliaLang#17)

* Add exercise: anagram

* Anagram exercise: use AbstractString as suggested

* Fix exercise anagram template file: use AbstractString

config.json

@@ -5,14 +5,25 @@
   "active": false,
   "test_pattern": "TODO",
   "exercises": [
-		{
+    {
       "slug": "leap",
       "difficulty": 1,
       "topics": [
         "control-flow (conditionals)",
 				"integers", 
 				"mathematics"
       ]
+    },
+    {
+      "slug": "anagram",
+      "difficulty": 2,
+      "topics": [
+        "control-flow (loops)",
+        "arrays",
+        "strings",
+        "sorting",
+        "filtering"
+      ]
     }
   ],
   "deprecated": [

exercises/anagram/anagram.jl

@@ -0,0 +1,4 @@
+function detect_anagrams(subject::AbstractString, candidates::AbstractArray)
+
+end
+

exercises/anagram/example.jl

@@ -0,0 +1,43 @@
+# Anagrams are two or more words that composed of the same characters but in a different order
+
+function is_anagram(s1::AbstractString, s2::AbstractString)
+  # Disable case sensitivity
+  s1 = lowercase(s1)
+  s2 = lowercase(s2)
+
+  # Similar and different-length strings are not anagrams
+  if length(s1) != length(s2) || s1 == s2
+    return false
+  end
+
+  # Calculate count of every character in the first string
+  chr_count = Dict()
+  for c in s1
+    chr_count[c] = get(chr_count, c, 0) + 1
+  end
+
+  # Reduce the count by every character from the second string
+  for c in s2
+    t = get(chr_count, c, 0) - 1
+    if t < 0
+      # Got character that not exist in the first string
+      return false
+    else
+      chr_count[c] = t
+    end
+  end
+
+  # Check all counts to be zeroes
+  return all(i->(i==0), values(chr_count))
+end
+
+function detect_anagrams(subject::AbstractString, candidates::AbstractArray)
+  result = []
+  for candidate = candidates
+    if is_anagram(subject, candidate)
+      push!(result, candidate)
+    end
+  end
+  result
+end
+

exercises/anagram/runtests.jl

@@ -0,0 +1,68 @@
+using Base.Test
+
+include("anagram.jl")
+
+@testset "no matches" begin
+  @test detect_anagrams("diasper", ["hello", "world", "zombies", "pants"]) == []
+end
+
+@testset "detects simple anagram" begin
+  @test detect_anagrams("ant", ["tan", "stand", "at"]) == ["tan"]
+end
+
+@testset "does not detect false positives" begin
+  @test detect_anagrams("galea", ["eagle"]) == []
+end
+
+@testset "detects multiple anagrams" begin
+  @test detect_anagrams("master", ["stream", "pigeon", "maters"]) == ["stream", "maters"]
+end
+
+@testset "does not detect anagram subsets" begin
+  @test detect_anagrams("good", ["dog", "goody"]) == []
+end
+
+@testset "detects anagram" begin
+  @test detect_anagrams("listen", ["enlists", "google", "inlets", "banana"]) == ["inlets"]
+end
+
+@testset "detects multiple anagrams" begin
+  @test detect_anagrams("allergy", ["gallery", "ballerina", "regally", "clergy", "largely", "leading"]) == ["gallery", "regally", "largely"]
+end
+
+@testset "does not detect identical words" begin
+  @test detect_anagrams("corn", ["corn", "dark", "Corn", "rank", "CORN", "cron", "park"]) == ["cron"]
+end
+
+@testset "does not detect non-anagrams with identical checksum" begin
+  @test detect_anagrams("mass", ["last"]) == []
+end
+
+@testset "detects anagrams case-insensitively" begin
+  @test detect_anagrams("Orchestra", ["cashregister", "Carthorse", "radishes"]) == ["Carthorse"]
+end
+
+@testset "detects anagrams using case-insensitive subject" begin
+  @test detect_anagrams("Orchestra", ["cashregister", "carthorse", "radishes"]) == ["carthorse"] 
+end
+
+@testset "detects anagrams using case-insensitive possible matches" begin
+  @test detect_anagrams("orchestra", ["cashregister", "Carthorse", "radishes"]) == ["Carthorse"]
+end
+
+@testset "does not detect a word as its own anagram" begin
+  @test detect_anagrams("banana", ["Banana"]) == []
+end
+
+@testset "does not detect a anagram if the original word is repeated" begin
+  @test detect_anagrams("go", ["go Go GO"]) == []
+end
+
+@testset "anagrams must use all letters exactly once" begin
+  @test detect_anagrams("tapper", ["patter"]) == []
+end
+
+@testset "capital word is not own anagram" begin
+  @test detect_anagrams("BANANA", ["Banana"]) == []
+end
+