LeetCode-in-All
347. Top K Frequent Elements
Medium
Given an integer array nums and an integer k, return the k most frequent elements. You may return the answer in any order.
Example 1:
Input: nums = [1,1,1,2,2,3], k = 2
Output: [1,2]
Example 2:
Input: nums = [1], k = 1
Output: [1]
Constraints:
1 <= nums.length <= 105-104 <= nums[i] <= 104kis in the range[1, the number of unique elements in the array].- It is guaranteed that the answer is unique.
Follow up: Your algorithm’s time complexity must be better than O(n log n), where n is the array’s size.
Solution
class Solution {
List<int> topKFrequent(List<int> nums, int k) {
Map<int, int> freq = {} ;
int n = nums.length ;
for(int i in nums)freq[i]=(freq[i] ?? 0) + 1;
List<List<int>> cont=
List.generate(n+1, (i) => [], growable: false);
freq.forEach((k, v) => cont[v].add(k));
List<int> res=[];
for(int i=n; i>0; i--)
if(cont[i]!= null)
for(int j in cont[i]){
res.add(j);
k--;
if(k ==0)return res;
}
return res;
}
}