Space - Katie

lib/exercises.rb

@@ -1,19 +1,47 @@
 
 # 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) where m is the num words and n is longest num of characters in the words
+# Space Complexity: O(n)
 
 def grouped_anagrams(strings)
-  raise NotImplementedError, "Method hasn't been implemented yet!"
+  return [] if strings.empty?
+  hash_of_letter_groups_and_words = {}
+  strings.each do |word|
+    sorted_word = word.chars.sort
+    if hash_of_letter_groups_and_words.keys.include?(sorted_word)
+      hash_of_letter_groups_and_words[sorted_word].push(word)
+    else
+      hash_of_letter_groups_and_words[sorted_word] = [word]
+    end
+  end
+  return hash_of_letter_groups_and_words.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: ?
+# Time Complexity: O (n log n) 
+# Space Complexity: O (n)
 def top_k_frequent_elements(list, k)
-  raise NotImplementedError, "Method hasn't been implemented yet!"
+  return [] if list.empty?
+  hash_occurences = {}
+  list.each do |num|
+    if hash_occurences.keys.include?(num)
+      hash_occurences[num] += 1
+    else
+      hash_occurences[num] = 1
+    end
+  end
+
+  sorted_array = hash_occurences.sort_by{|k,v| -v}
+
+  k_most_frequent_elements = []
+
+  k.times do |i|
+    k_most_frequent_elements.push(sorted_array[i][0])
+  end
+
+  return k_most_frequent_elements
 end