Angela

lib/exercises.rb

@@ -2,19 +2,56 @@
 
 # This method will return an array of arrays.
 # Each subarray will have strings which are anagrams of each other
-# Time Complexity: ?
-# Space Complexity: ?
+# Time Complexity: O(n) where n is the size of the strings array
+# Space Complexity: O(n) where n is the size of the strings array
 
 def grouped_anagrams(strings)
-  raise NotImplementedError, "Method hasn't been implemented yet!"
+  return strings if strings.length == 1 || strings.length == 0
+
+  grouped_words_hash = {}
+  strings.each do |word|
+    check_word = word.chars.sort.join
+    if grouped_words_hash[check_word].nil?
+      grouped_words_hash[check_word] = [word]
+    else
+      grouped_words_hash[check_word].push(word)
+    end
+  end
+
+  grouped_words_array = []
+  grouped_words_hash.each do |sorted_word, array|
+    grouped_words_array.push(array)
+  end
+  return grouped_words_array
 end
 
 # This method will return the k most common elements
 # in the case of a tie it will select the first occuring element.
-# Time Complexity: ?
-# Space Complexity: ?
+# Time Complexity: O(nlogn) because of the sort_by algorithm
+# Space Complexity: O(n) where n is the size of list
 def top_k_frequent_elements(list, k)
-  raise NotImplementedError, "Method hasn't been implemented yet!"
+  return list if list.length == 0
+
+  track_common_elements = {}
+  list.each do |element|
+    if track_common_elements[element].nil?
+      track_common_elements[element] = 1
+    else
+      track_common_elements[element] += 1
+    end
+  end
+
+
+  common_elements_array = track_common_elements.sort_by {|num, occurence| -occurence}
+  result = []
+  i = 0
+  common_elements_array.each do |one_num_array| 
+    if i < k
+      result.push(one_num_array[0])
+    end
+    i += 1
+  end
+  return result
 end
 
 

test/exercises_test.rb

@@ -68,7 +68,7 @@
     end
   end
 
-  xdescribe "top_k_frequent_elements" do
+  describe "top_k_frequent_elements" do
     it "works with example 1" do
       # Arrange
       list = [1,1,1,2,2,3]