Update 347._Top_K_Frequent_Elements.md

Author: 0xkookoo

docs/Leetcode_Solutions/347._Top_K_Frequent_Elements.md

@@ -1,21 +1,30 @@
-# 1. Two Sum 两数之和
+# 347. Top K Frequent Elements
 
-**<font color=red>难度: Easy</font>**
+**<font color=red>难度: Medium</font>**
 
 ## 刷题内容
 
 > 原题连接
 
-* https://leetcode.com/problems/two-sum
-* https://leetcode-cn.com/problems/two-sum/description
+* https://leetcode.com/problems/top-k-frequent-elements/description/
 
 > 内容描述
 
 ```
-给定 nums = [2, 7, 11, 15], target = 9
+Given a non-empty array of integers, return the k most frequent elements.
 
-因为 nums[0] + nums[1] = 2 + 7 = 9
-所以返回 [0, 1]
+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.
 ```
 
 ## 解题方案