water - mackenzie

lib/exercises.rb

@@ -1,19 +1,43 @@
 
 # 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(nm(log m)) + O(n) (sort_by for each string + length of strings array)
+# Space Complexity: O(n) (hash size increases with input array length, no other data structures made)
 
 def grouped_anagrams(strings)
-  raise NotImplementedError, "Method hasn't been implemented yet!"
+  anagrams = {}
+  strings.each do |string|
+    abc_string = string.chars.sort_by(&:downcase).join
+    if !anagrams[abc_string]
+      anagrams[abc_string] = []
+    end
+    anagrams[abc_string] << string
+  end 
+  puts anagrams
+  return anagrams.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) + O(n logn) ( sort is nlogn, list.each is n, map is n)
+# Space Complexity: O(n) (multiple same sized arrays)
 def top_k_frequent_elements(list, k)
-  raise NotImplementedError, "Method hasn't been implemented yet!"
+  # raise NotImplementedError, "Method hasn't been implemented yet!"
+  return list if list.empty?
+
+  counted = {}
+  list.each do |num|
+    if counted[num] 
+      counted[num] += 1
+    else 
+      counted[num] = 1
+    end
+  end
+
+  sorted = counted.sort {|a,b| b[1]<=>a[1]}
+  keys = sorted.map { |n| n[0] }
+
+  return keys.slice(0, k)
 end