Earth - Anya

lib/exercises.rb

@@ -1,19 +1,41 @@
 
 # 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 * m) n is the length of the array, m is the max length of string within the array. 
+# Could pull chars method to run first on each element of strings, for O(n) n being the longest string or array.
+# Space Complexity: O(n)
 
 def grouped_anagrams(strings)
-  raise NotImplementedError, "Method hasn't been implemented yet!"
+  return [] if strings.nil?
+  return [] if strings.empty?
+
+  counts_hash = Hash.new([])
+  strings.each do |string|
+    counts_hash[string.chars.sort] += [string]
+  end
+  return counts_hash.map {|k, v| v}
 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(n) n is list length
+# Space Complexity: O(n^2 * k) is that right?
 def top_k_frequent_elements(list, k)
-  raise NotImplementedError, "Method hasn't been implemented yet!"
+  return [] if list.nil?
+  return [] if list.empty?
+
+  counts_hash = Hash.new(0) # space = O(n)
+  list.each do |num|
+    counts_hash[num] += 1
+  end
+
+  sorted_values_2d = counts_hash.sort_by {|k, v| -v} # space = O(n)
+
+  k_most_common_ele = [] # space = O(k)
+  k.times do |i|
+    k_most_common_ele << sorted_values_2d[i][0]
+  end
+  return k_most_common_ele
 end