Description
Design a search autocomplete system for a search engine. Users may input a sentence (at least one word and end with a special character ‘#’). For each character they type except ‘#’, you need to return the top 3 historical hot sentences that have prefix the same as the part of sentence already typed. Here are the specific rules:
The hot degree for a sentence is defined as the number of times a user typed the exactly same sentence before.
The returned top 3 hot sentences should be sorted by hot degree (The first is the hottest one). If several sentences have the same degree of hot, you need to use ASCII-code order (smaller one appears first).
If less than 3 hot sentences exist, then just return as many as you can.
When the input is a special character, it means the sentence ends, and in this case, you need to return an empty list.
Your job is to implement the following functions:
The constructor function:
AutocompleteSystem(String[] sentences, int[] times): This is the constructor. The input is historical data. Sentences is a string array consists of previously typed sentences. Times is the corresponding times a sentence has been typed. Your system should record these historical data.
Now, the user wants to input a new sentence. The following function will provide the next character the user types:
List
Example
1 | Example: |
Note:
The input sentence will always start with a letter and end with ‘#’, and only one blank space will exist between two words.
The number of complete sentences that to be searched won’t exceed 100. The length of each sentence including those in the historical data won’t exceed 100.
Please use double-quote instead of single-quote when you write test cases even for a character input.
Please remember to RESET your class variables declared in class AutocompleteSystem, as static/class variables are persisted across multiple test cases. Please see here for more details.
Solution
Solution 1: Basic Solution, HashMap1
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
58class AutocompleteSystem {
String[] sentences;
int[] times;
String search;
HashMap<String, Integer> history;
public AutocompleteSystem(String[] sentences, int[] times) {
history = new HashMap<>();
for (int i = 0; i < sentences.length; i++){
history.put(sentences[i], times[i]);
}
search = "";
}
public List<String> input(char c) {
if (c == '#'){
if (history.containsKey(search)) history.put(search, history.get(search)+1);
else history.put(search, 1);
search = "";
return new ArrayList<String>();
}
search += c;
int len = search.length();
TreeMap<Integer, PriorityQueue<String>> map = new TreeMap<>((a,b) -> b-a);
for (String s: history.keySet()){
if (s.length() >= len){
String tmp = s.substring(0, len);
if (tmp.equals(search)){
if (map.containsKey(history.get(s))){
PriorityQueue<String> pq = map.get(history.get(s));
pq.offer(s);
map.put(history.get(s), pq);
}
else {
PriorityQueue<String> pq = new PriorityQueue<>();
pq.offer(s);
map.put(history.get(s),pq);
}
}
}
}
List<String> res = new ArrayList<>();
for (int it: map.keySet()){
PriorityQueue<String> pq = map.get(it);
while (!pq.isEmpty()){
res.add(pq.poll());
if (res.size() == 3) return res;
}
}
return res;
}
}
/**
* Your AutocompleteSystem object will be instantiated and called as such:
* AutocompleteSystem obj = new AutocompleteSystem(sentences, times);
* List<String> param_1 = obj.input(c);
*/
Solution 2: Trie Tree1
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
67
68
69
70
71
72
73
74
75
76public class AutocompleteSystem {
class TrieNode {
Map<Character, TrieNode> children;
Map<String, Integer> counts;
boolean isWord;
public TrieNode() {
children = new HashMap<Character, TrieNode>();
counts = new HashMap<String, Integer>();
isWord = false;
}
}
class Pair {
String s;
int c;
public Pair(String s, int c) {
this.s = s; this.c = c;
}
}
TrieNode root;
String prefix;
public AutocompleteSystem(String[] sentences, int[] times) {
root = new TrieNode();
prefix = "";
for (int i = 0; i < sentences.length; i++) {
add(sentences[i], times[i]);
}
}
private void add(String s, int count) {
TrieNode curr = root;
for (char c : s.toCharArray()) {
TrieNode next = curr.children.get(c);
if (next == null) {
next = new TrieNode();
curr.children.put(c, next);
}
curr = next;
curr.counts.put(s, curr.counts.getOrDefault(s, 0) + count);
}
curr.isWord = true;
}
public List<String> input(char c) {
if (c == '#') {
add(prefix, 1);
prefix = "";
return new ArrayList<String>();
}
prefix = prefix + c;
TrieNode curr = root;
for (char cc : prefix.toCharArray()) {
TrieNode next = curr.children.get(cc);
if (next == null) {
return new ArrayList<String>();
}
curr = next;
}
PriorityQueue<Pair> pq = new PriorityQueue<>((a, b) -> (a.c == b.c ? a.s.compareTo(b.s) : b.c - a.c));
for (String s : curr.counts.keySet()) {
pq.add(new Pair(s, curr.counts.get(s)));
}
List<String> res = new ArrayList<String>();
for (int i = 0; i < 3 && !pq.isEmpty(); i++) {
res.add(pq.poll().s);
}
return res;
}
}