diff --git a/hash_practice/exercises.py b/hash_practice/exercises.py
index 48bf95e..ff43402 100644
--- a/hash_practice/exercises.py
+++ b/hash_practice/exercises.py
@@ -2,18 +2,43 @@
 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)
+        Space Complexity: O(n)
     """
-    pass
+    hash_table = {}
+    for str in strings:
+        key = ''.join(sorted(str))
+        if key in hash_table.keys():
+            hash_table[key].append(str)
+        else:
+            hash_table[key] = []
+            hash_table[key].append(str)
+
+    result = []
+    for key, value in hash_table.items():
+        result.append(value)
+    return result
+
 
 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
+    frequency = {}
+    for num in nums:
+        if num not in frequency:
+            frequency[num] = 1
+        else:
+            frequency[num] = frequency[num] + 1
+
+    frequency = dict(
+        sorted(frequency.items(), key=lambda x: x[1], reverse=True))
+
+    result = list(frequency.keys())[:k]
+
+    return result
 
 
 def valid_sudoku(table):
@@ -22,8 +47,21 @@ 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
-
+    seen = set()
+    for i in range(9):
+        for j in range(9):
+            number = str(table[i][j])
+            if number != '.':
+                row = number + 'in row' + str(i)
+                col = number + 'in col' + str(j)
+                # // for integer
+                block = number + 'in block' + str(i//3) + str(j//3)
+                if row in seen or col in seen or block in seen:
+                    return False
+                seen.add(row)
+                seen.add(col)
+                seen.add(block)
+    return True