Top K Frequent Words In DataStream高频题其它公司也喜欢考

private Map<String, Integer> words = null;
private NavigableSet<String> topk = null;
private int k;

private Comparator<String> myComparator = new Comparator<String>() {
public int compare(String left, String right) {
if (left.equals(right))
return 0;

int left_count = words.get(left);
int right_count = words.get(right);
if (left_count != right_count) {
return right_count - left_count;
}
return left.compareTo(right);
}
};

public TopKFrequentWordsInDataStream(int k) {
// initialize your data structure here
this.k = k;
words = new HashMap<String, Integer>();
topk = new TreeSet<String>(myComparator);
}

public void add(String word) {
// Write your code here
if (words.containsKey(word)) {
if (topk.contains(word))
topk.remove(word);
words.put(word, words.get(word) + 1);
} else {
words.put(word, 1);
}

topk.add(word);
if (topk.size() > k) {
topk.pollLast();
}
}

public List<String> topk() {
// Write your code here
List<String> results = new ArrayList<String>();
Iterator it = topk.iterator();
while(it.hasNext()) {
String str = (String)it.next();
results.add(str);
}
return results;
}