Jessica

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 logn) where n is the length of the strings in the strings element
+# Space Complexity: O(n) where n is the length of the input
 def grouped_anagrams(strings)
-  raise NotImplementedError, "Method hasn't been implemented yet!"
+  return [] if strings == []
+  anagrams = {}
+
+  strings.each_with_index do |string, i|
+    sorted_string = string.split("").sort.join("").downcase
+    if anagrams[sorted_string]
+      anagrams[sorted_string] << string
+    else
+      anagrams[sorted_string] = [string]
+    end
+  end
+
+  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) where n is the length of list
+# Space Complexity: O(n) where n is the length of the list
 def top_k_frequent_elements(list, k)
-  raise NotImplementedError, "Method hasn't been implemented yet!"
+  return [] if list == []
+
+  frequency = {}
+  list.each do |element|
+    if frequency[element]
+      frequency[element] += 1
+    else
+      frequency[element] = 1
+    end
+  end
+
+  k_frequent_elements = []
+
+  k.times do |i|
+    max_freq = 0
+    max_freq_element = nil
+    frequency.each do |element, freq|
+      if freq > max_freq
+        max_freq = freq
+        max_freq_element = element
+      end
+    end
+    k_frequent_elements << max_freq_element
+    frequency[max_freq_element] = 0 if max_freq_element
+  end
+
+  return k_frequent_elements
 end
 
 
@@ -26,5 +63,131 @@ def top_k_frequent_elements(list, k)
 # Time Complexity: ?
 # Space Complexity: ?
 def valid_sudoku(table)
-  raise NotImplementedError, "Method hasn't been implemented yet!"
+  subgrids = {}
+
+  # return false if any element is repeated in a row
+  table.each do |row|
+    row_count = {}
+    row.each do |element|
+      if row_count[element]
+        return false unless element == "."
+      else
+        row_count[element] = 1
+      end
+    end
+  end
+
+  # return false if any element is repeated in a column
+  columns = {
+    0 => {},
+    1 => {},
+    2 => {},
+    3 => {},
+    4 => {},
+    5 => {},
+    6 => {},
+    7 => {},
+    8 => {},
+  }
+  table.each do |row|
+    row.each_with_index do |element, index|
+      if columns[index][element]
+        return false unless element == "."
+      else
+        columns[index][element] = 1
+      end
+    end
+  end
+
+  first_subgrid = {}
+  second_subgrid = {}
+  third_subgrid = {}
+
+  table[0..2].each do |row|
+    row[0..2].each do |element|
+      if first_subgrid[element]
+        return false unless element == "."
+      else
+        first_subgrid[element] = 1
+      end
+    end
+
+    row[3..5].each do |element|
+      if second_subgrid[element]
+        return false unless element == "."
+      else
+        second_subgrid[element] = 1
+      end
+    end
+
+    row[6..8].each do |element|
+      if third_subgrid[element]
+        return false unless element == "."
+      else
+        third_subgrid[element] = 1
+      end
+    end
+  end
+
+  first_subgrid = {}
+  second_subgrid = {}
+  third_subgrid = {}
+
+  table[3..5].each do |row|
+    row[0..2].each do |element|
+      if first_subgrid[element]
+        return false unless element == "."
+      else
+        first_subgrid[element] = 1
+      end
+    end
+
+    row[3..5].each do |element|
+      if second_subgrid[element]
+        return false unless element == "."
+      else
+        second_subgrid[element] = 1
+      end
+    end
+
+    row[6..8].each do |element|
+      if third_subgrid[element]
+        return false unless element == "."
+      else
+        third_subgrid[element] = 1
+      end
+    end
+  end
+
+  first_subgrid = {}
+  second_subgrid = {}
+  third_subgrid = {}
+
+  table[6..8].each do |row|
+    row[0..2].each do |element|
+      if first_subgrid[element]
+        return false unless element == "."
+      else
+        first_subgrid[element] = 1
+      end
+    end
+
+    row[3..5].each do |element|
+      if second_subgrid[element]
+        return false unless element == "."
+      else
+        second_subgrid[element] = 1
+      end
+    end
+
+    row[6..8].each do |element|
+      if third_subgrid[element]
+        return false unless element == "."
+      else
+        third_subgrid[element] = 1
+      end
+    end
+  end
+
+  return true
 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]
@@ -131,7 +131,7 @@
 
   end
 
-  xdescribe "valid sudoku" do
+  describe "valid sudoku" do
     it "works for the table given in the README" do
       # Arrange
       table = [