Top K Frequent Elements

Author: weiy

Diff for: Array/TopKFrequentElements.py

@@ -0,0 +1,44 @@
+"""
+Given a non-empty array of integers, return the k most frequent elements.
+
+Example 1:
+
+Input: nums = [1,1,1,2,2,3], k = 2
+Output: [1,2]
+Example 2:
+
+Input: nums = [1], k = 1
+Output: [1]
+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.
+
+思路：
+首先是计算出每个数字出现的频率，之后排序频率，输出最高的k位。
+
+字典（哈希表），sorted（排序）。
+
+beat 88%
+
+测试用例：
+https://leetcode.com/problems/top-k-frequent-elements/description/
+
+"""
+class Solution(object):
+    def topKFrequent(self, nums, k):
+        """
+        :type nums: List[int]
+        :type k: int
+        :rtype: List[int]
+        """
+        
+        nums_dict = {}
+        
+        for i in nums:
+            try:
+                nums_dict[i] += 1
+            except KeyError:
+                nums_dict[i] = 1
+        
+        return sorted(nums_dict, key=lambda x: nums_dict[x], reverse=True)[:k]