347. Top K Frequent Elements（对字典排序）

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.

class Solution:
    def topKFrequent(self, nums, k):
        """
        :type nums: List[int]
        :type k: int
        :rtype: List[int]
        """
        dic = {}
        for i in nums:
            if i not in dic:
                dic[i] = 1
            else:
                dic[i] += 1
        ans = sorted(dic.items(),key=lambda x:x[1],reverse=True)
        # print(ans)
        res = []
        for i in range(k):
                res.append(ans[i][0])
        return res