diff --git a/hash_practice/exercises.py b/hash_practice/exercises.py
index 48bf95e..0b5b660 100644
--- a/hash_practice/exercises.py
+++ b/hash_practice/exercises.py
@@ -2,18 +2,44 @@
 def grouped_anagrams(strings):
     """ 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^2)
+        Space Complexity: O(n)
     """
-    pass
+    string_dict = {}
+    for string in strings:
+        key = ''.join(sorted(string))
+
+        if key in string_dict.keys():
+            string_dict[key].append(string)
+        else:
+            string_dict[key] = [string]
+        
+    return list(string_dict.values())
 
 def top_k_frequent_elements(nums, k):
     """ 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 log n)??
+        Space Complexity: O(n)
     """
-    pass
+    frequency_map = {}
+    return_list = []
+
+    for num in nums:
+        if num in frequency_map:
+            frequency_map[num] += 1
+        else:
+            frequency_map[num] = 1
+
+    max_values = sorted(frequency_map.values(), reverse=True)
+        
+    for key, value in frequency_map.items():
+        if value in max_values[:k] and (len(return_list) < k):
+            return_list.append(key)
+
+    return return_list
+
+
 
 
 def valid_sudoku(table):
@@ -22,8 +48,38 @@ def valid_sudoku(table):
         Each element can either be a ".", or a digit 1-9
         The same digit cannot appear twice or more in the same 
         row, column or 3x3 subgrid
-        Time Complexity: ?
-        Space Complexity: ?
+        Time Complexity: O(n^2)
+        Space Complexity: O(n)
     """
-    pass
+    # check if the input has too many rows
+    if len(table) > 9:
+        return False
+    for i in range(len(table)):
+        row_dictionary = {}
+        column_dictionary = {}
+        subgrid_dictionary = {}
+
+        # check if the input has too many columns
+        if len(table[i]) > 9:
+            return False
+        
+        for j in range(len(table[i])):
+            # check row
+            if table[i][j] != "." and table[i][j] in row_dictionary:
+                return False
+            row_dictionary[table[i][j]] = "yay!"
+
+            # check column
+            if table[j][i] != "." and table[j][i] in column_dictionary:
+                return False
+            column_dictionary[table[j][i]] = "yay!"
+
+            # check sub-grid
+            # ????
+    return True
+
+            
+
+
+