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topKFrequent.py
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topKFrequent.py
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# https://leetcode.com/problems/top-k-frequent-elements/description/
# 347. Top K Frequent Elements
# 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.
#################
## solution 1 ###
#################
from collections import Counter as c
def topKFrequent(nums, k):
"""
:type nums: List[int]
:type k: int
:rtype: List[int]
"""
count = []
for key, val in c(nums).items():
count.append([val, key])
count.sort(reverse=True)
res = []
i = 0
while i < k:
res.append(count[i][1])
i += 1
return res
#################
## solution 2###
#################
from collections import Counter as c
def topKFrequent(nums, k):
"""
:type nums: List[int]
:type k: int
:rtype: List[int]
"""
return [num for num, count in c(nums).most_common(k)]
assert topKFrequent([1,1,1,2,2,3], 2) == [1, 2]
assert topKFrequent([1], 1) == [1]