diff --git a/hash_practice/exercises.py b/hash_practice/exercises.py
index 48bf95e..35d0f1b 100644
--- a/hash_practice/exercises.py
+++ b/hash_practice/exercises.py
@@ -2,19 +2,52 @@
 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
+    if not strings:
+        return []
+    anagrams = {}
+    for string in strings:
+        sorted_string = "".join(sorted(string))
+        if sorted_string in anagrams:
+            anagrams[sorted_string].append(string)
+        else:
+            anagrams[sorted_string] = [string]
+    return list(anagrams.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)
+        Space Complexity: O(n)
     """
-    pass
+    if not nums:
+        return []
+    counts = {}
+    for num in nums:
+        if num in counts:
+            counts[num] += 1
+        else:
+            counts[num] = 1
+    sorted_counts = sorted(counts.items(), key=lambda x: x[1], reverse=True)
+    return [x[0] for x in sorted_counts[:k]]
 
+def valid_row(row):
+    if not row:
+        return False
+    for i in range(1, 10):
+        if str(i) not in row:
+            return False
+    return True
+
+def valid_subgrid(subgrid):
+    if not subgrid:
+        return False
+    for row in subgrid:
+        if not valid_row(row):
+            return False
+    return True
 
 def valid_sudoku(table):
     """ This method will return the true if the table is still
@@ -22,8 +55,22 @@ 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
+
+    if not table:
+        return False
+    for row in table:
+        if not valid_row(row):
+            return False
+    for col in zip(*table):
+        if not valid_row(col):
+            return False
+    for i in range(0, 9, 3):
+        for j in range(0, 9, 3):
+            if not valid_subgrid(table[i:i+3], table[j:j+3]):
+                return False
+    return True
+