Time - Denisse

lib/exercises.rb

@@ -1,19 +1,52 @@
 
 # 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: a lot
+# Space Complexity: O(n)
 
 def grouped_anagrams(strings)
-  raise NotImplementedError, "Method hasn't been implemented yet!"
+  hash = {}
+
+  strings.each do | string | 
+
+   a_key = string.chars.sort
+
+   if hash[a_key]
+     hash[a_key] << string 
+   else
+     hash[a_key] = [string]
+   end
+  end 
+
+   return hash.values
 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: ?
+# resource: https://stackoverflow.com/questions/4264133/descending-sort-by-value-of-a-hash-in-ruby
 def top_k_frequent_elements(list, k)
-  raise NotImplementedError, "Method hasn't been implemented yet!"
+  # Hash.new(0) sets default value for any key to 0, while {} sets nil
+  hash = Hash.new(0)
+  k_array = []
+
+  return [] if list.empty?
+
+  # populate the hash and count occurrence
+  list.each do |num|
+    hash[num] += 1
+  end
+
+  # set hash's values in descending order
+  descending_hash = hash.sort_by {|key, value| -value}
+
+  # populate the array with most common elements dictated by k
+  k.times do |i|
+    k_array << descending_hash[i][0]
+  end
+
+  return k_array
 end