347. Top K Frequent Elements

Difficulty: Medium
21 / 21 test cases passed.
Runtime: 112 ms
Memory Usage: 18.5 MB

Author: YuriSpiridonov

Medium/347.TopKFrequentElements.py

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+"""
+    Given a non-empty array of integers, return the k most frequent elements.
+
+    Example:
+    Input: nums = [1,1,1,2,2,3], k = 2
+    Output: [1,2]
+
+    Note:
+        - You may assume k is always valid, 1 ≤ k ≤ number of unique elements.
+        - Your algorithm's time complexity must be better than O(n log n), where 
+          n is the array's size.
+        - It's guaranteed that the answer is unique, in other words the set of 
+          the top k frequent elements is unique.
+        - You can return the answer in any order.
+"""
+#Difficulty: Medium
+#21 / 21 test cases passed.
+#Runtime: 112 ms
+#Memory Usage: 18.5 MB
+
+#Runtime: 112 ms, faster than 51.73% of Python3 online submissions for Top K Frequent Elements.
+#Memory Usage: 18.5 MB, less than 8.25% of Python3 online submissions for Top K Frequent Elements.
+
+class Solution:
+    def topKFrequent(self, nums: List[int], k: int) -> List[int]:
+        d = {}
+        for num in nums:
+            if num in d.keys():
+                d[num] += 1
+            else:
+                d[num] = 1
+        return [key[0] for key in sorted(d.items(), key=lambda item: item[1])][-k:]