Problem:
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.
思路：
Solution (C++):
vector<int> topKFrequent(vector<int>& nums, int k) {
unordered_map<int, int> frequency;
for (auto num : nums) ++frequency[num];
priority_queue<pair<int, int>> pri_que;
vector<int> res;
for (auto it = frequency.begin(); it != frequency.end(); ++it) {
pri_que.push(make_pair(it->second, it->first));
if (pri_que.size() > frequency.size() - k) {
res.push_back(pri_que.top().second);
pri_que.pop();
}
}
return res;
}
性能：
Runtime: 24 ms Memory Usage: 9.2 MB
思路：
Solution (C++):
性能：
Runtime: ms Memory Usage: MB
