C15 Paper--Weishan

hash_practice/exercises.py

@@ -2,18 +2,46 @@
 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
+    anagram_dict = {}
+    output = []
+
+    for word in strings:
+        word_key = "".join(sorted(word))
+        if (word_key in anagram_dict):
+            anagram_dict[word_key].append(word)
+        else:
+            anagram_dict[word_key] = [word]
+
+    for word_key in anagram_dict:
+        output.append(anagram_dict[word_key])
+
+    return output
 
 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(nk)
+        Space Complexity: O(n)
     """
-    pass
+    frequency_dict = {}
+    result = []
+    if not nums:
+        return []
+
+    for num in nums:
+        if num in frequency_dict:
+            frequency_dict[num] += 1
+        else:
+            frequency_dict[num] = 1
+
+    for i in range(k):
+        highest_value = max(frequency_dict, key=frequency_dict.get)
+        result.append(highest_value)
+        frequency_dict.pop(highest_value)
+    return result
 
 
 def valid_sudoku(table):
@@ -25,5 +53,38 @@ def valid_sudoku(table):
         Time Complexity: ?
         Space Complexity: ?
     """
-    pass
+    for row in table:
+        row_dict = {}
+        for square in row:
+            if square != ".":
+                if square not in row_dict:
+                    row_dict[square] = 1
+                else:
+                    return False
+
+    for col in range(0, len(table)):
+        col_dict = {}
+        for square in table[col]:
+            if square != ".":
+                if square not in col_dict:
+                    col_dict[square] = 1
+                else:
+                    return False
+
+    for row in range(3):
+        for col in range(3):
+            block_dict = {}
+            block = [
+                table[3*row][3*col:3*col+3],
+                table[3*row+1][3*col:3*col+3],
+                table[3*row+2][3*col:3*col+3]
+            ]
+            for segment in block:
+                for elem in segment:
+                    if elem != ".":
+                        if elem in block_dict:
+                            return False
+                        else:
+                            block_dict[elem] = 1
+    return True