-
Notifications
You must be signed in to change notification settings - Fork 2
/
TopKFrequentWords.java
66 lines (57 loc) · 2.08 KB
/
TopKFrequentWords.java
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
package Leetcode;
import java.util.*;
/**
* @author kalpak
*
* Given a non-empty list of words, return the k most frequent elements.
*
* Your answer should be sorted by frequency from highest to lowest. If two words have the same frequency, then the word with the lower alphabetical order comes first.
*
* Example 1:
*
* Input: ["i", "love", "leetcode", "i", "love", "coding"], k = 2
* Output: ["i", "love"]
* Explanation: "i" and "love" are the two most frequent words.
* Note that "i" comes before "love" due to a lower alphabetical order.
*
* Example 2:
*
* Input: ["the", "day", "is", "sunny", "the", "the", "the", "sunny", "is", "is"], k = 4
* Output: ["the", "is", "sunny", "day"]
* Explanation: "the", "is", "sunny" and "day" are the four most frequent words,
* with the number of occurrence being 4, 3, 2 and 1 respectively.
*
* Note:
*
* You may assume k is always valid, 1 ≤ k ≤ number of unique elements.
* Input words contain only lowercase letters.
*
* Follow up:
*
* Try to solve it in O(n log k) time and O(n) extra space.
*/
public class TopKFrequentWords {
public static List<String> topKFrequent(String[] words, int k) {
Map<String, Integer> wordFrequency = new HashMap<>();
PriorityQueue<String> pq = new PriorityQueue<>((word1, word2) ->
wordFrequency.get(word1).equals(wordFrequency.get(word2)) ?
word2.compareTo(word1) : wordFrequency.get(word1) - wordFrequency.get(word2));
List<String> result = new ArrayList<>();
for(String word : words) {
wordFrequency.put(word, wordFrequency.getOrDefault(word, 0) + 1);
}
for(String word : wordFrequency.keySet()) {
pq.offer(word);
if(pq.size() > k)
pq.poll();
}
while(!pq.isEmpty()) {
result.add(0, pq.poll());
}
return result;
}
public static void main(String[] args) {
String[] arr = new String[]{"i", "love", "leetcode", "i", "love", "coding"};
System.out.println(topKFrequent(arr, 2));
}
}