347. Top K Frequent Elements

Given a non-empty array of integers, return the k most frequent elements.

For example,

Given

[1,1,1,2,2,3]

and k = 2, return

[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.

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利用python可以简单实现：

代码如下：

class Solution(object):

    def topKFrequent(self, nums, k):

        """

        :type nums: List[int]

        :type k: int

        :rtype: List[int]

        """

        m1={}

        for temp in nums:

            if temp not in m1.keys():

                m1[temp]=1

            else:

                m1[temp]+=1

        m1=sorted(m1.iteritems(),key=lambda a:a[1],reverse=True)

        result=[]

        count=0

        for temp in m1:

            if count<k:

                result.append(temp[0])

                count+=1

            else:

                break

        return result