347. Top K Frequent Elements【M】【VIP】【字典排序】

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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这个其实挺简单，就是用hash，然后再排序

class Solution(object):
    def topKFrequent(self, nums, k):
        
        dic = {}
        
        for i in nums:
            dic[i] = dic.get(i,0) + 1
        
        #print dic.items()
        l = sorted(dic.iteritems(),key = lambda d:d[1], reverse = True)
        
        res = []
        for i in xrange(k):
            res += l[i][0],
        return res