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package design;
import java.util.*;
/**
* Created by gouthamvidyapradhan on 20/08/2017.
*
* <p>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:
*
* <p>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:
*
* <p>The constructor function:
*
* <p>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.
*
* <p>Now, the user wants to input a new sentence. The following function will provide the next
* character the user types:
*
* <p>List<String> input(char c): The input c is the next character typed by the user. The character
* will only be lower-case letters ('a' to 'z'), blank space (' ') or a special character ('#').
* Also, the previously typed sentence should be recorded in your system. The output will be the top
* 3 historical hot sentences that have prefix the same as the part of sentence already typed.
*
* <p>
*
* <p>Example: Operation: AutocompleteSystem(["i love you", "island","ironman", "i love leetcode"],
* [5,3,2,2]) The system have already tracked down the following sentences and their corresponding
* times: "i love you" : 5 times "island" : 3 times "ironman" : 2 times "i love leetcode" : 2 times
* Now, the user begins another search:
*
* <p>Operation: input('i') Output: ["i love you", "island","i love leetcode"] Explanation: There
* are four sentences that have prefix "i". Among them, "ironman" and "i love leetcode" have same
* hot degree. Since ' ' has ASCII code 32 and 'r' has ASCII code 114, "i love leetcode" should be
* in front of "ironman". Also we only need to output top 3 hot sentences, so "ironman" will be
* ignored.
*
* <p>Operation: input(' ') Output: ["i love you","i love leetcode"] Explanation: There are only two
* sentences that have prefix "i ".
*
* <p>Operation: input('a') Output: [] Explanation: There are no sentences that have prefix "i a".
*
* <p>Operation: input('#') Output: [] Explanation: The user finished the input, the sentence "i a"
* should be saved as a historical sentence in system. And the following input will be counted as a
* new search.
*
* <p>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.
*
* <p>Solution: Maintain a Trie (slightly modified) data-structure to all the input sentences where
* each node of the Trie is a node containing a hash-map of child character and node and a TreeSet
* containing the sorted order of all the possible child sentences starting from the current node.
* Maintain a cursor node 'curr' to indicate the current node of input, if the input character is
* absent then simply mark curr as null indicating no further auto-complete terms possible. On the
* other hand if the input character is present then simply pick the top 3 elements from the TreeSet
* object of curr node. Finally, use a StringBuilder to accumulate all the input characters and when
* a end of sentence is '#' is encountered simply update the trie with new sentence and degree.
*/
public class AutocompleteSystem {
private Map<String, Integer> hotTextMap; // Maintain a hash-map of sentences and degree
private Trie curr, trie, root;
private StringBuilder
currSentence; // StringBuilder class to maintain current input sentence (until '#')
/**
* Main method
*
* @param args
* @throws Exception
*/
public static void main(String[] args) throws Exception {
String[] sentences = {"i love you", "island", "ironman", "i love leetcode"};
int[] degree = {5, 3, 2, 2};
AutocompleteSystem autocomplete = new AutocompleteSystem(sentences, degree);
List<String> result = autocomplete.input('i');
result.forEach(System.out::println);
result = autocomplete.input(' ');
result.forEach(System.out::println);
result = autocomplete.input('a');
result.forEach(System.out::println);
result = autocomplete.input('#');
result.forEach(System.out::println);
}
/**
* Initialize the trie data-structure
*
* @param sentences array of sentences
* @param times degree
*/
public AutocompleteSystem(String[] sentences, int[] times) {
hotTextMap = new HashMap<>();
trie = new Trie();
for (int i = 0; i < sentences.length; i++) {
hotTextMap.put(sentences[i], times[i]);
trie.insert(sentences[i]);
trie.update(sentences[i]);
}
curr = trie;
root = trie;
currSentence = new StringBuilder();
}
/**
* Accept input and return hot-text for the current char
*
* @param c char
* @return List of top 3 hot-text
*/
public List<String> input(char c) {
List<String> result = new ArrayList<>();
if (c == '#') {
String sentence = currSentence.toString();
if (hotTextMap.containsKey(sentence)) {
// already a known sentence hence only update in necessary
hotTextMap.put(sentence, hotTextMap.get(sentence) + 1);
trie.update(sentence);
} else {
// insert a new sentence and update the degree
hotTextMap.put(sentence, 1);
trie.insert(sentence);
trie.update(sentence);
}
currSentence = new StringBuilder(); // reset StringBuilder
curr = root; // point to root of the trie
} else {
if (curr != null) {
if (curr.containsChild(c)) {
List<String> hotText = curr.getSubtrie(c).getTop3HotText();
hotText
.stream()
.forEach((x) -> result.add(currSentence.toString() + x)); // each node only returns
// the hot-text for the current and child nodes hence we have to attach the prefix string
curr = curr.getSubtrie(c);
} else {
curr =
null; // as soon as we encounter a empty node then set current to null indicating no
// further
// auto-complete terms are available
}
}
currSentence.append(c);
}
return result;
}
/** Class HotText to store the text and degree */
private class HotText {
private String text;
private int degree;
HotText(String text, int degree) {
this.text = text;
this.degree = degree;
}
private String getText() {
return text;
}
private int getDegree() {
return degree;
}
}
/** Class Trie */
private class Trie {
private Map<Character, Trie> map = new HashMap<>();
private TreeSet<HotText> hotText =
new TreeSet<>(
(HotText o1, HotText o2) -> {
int cmp = Integer.compare(o2.getDegree(), o1.getDegree());
return cmp == 0 ? o1.getText().compareTo(o2.getText()) : cmp;
});
/**
* Get hot-text
*
* @return HotText
*/
public TreeSet<HotText> getHotText() {
return hotText;
}
/**
* Return top 3 hottext
*
* @return hot text
*/
private List<String> getTop3HotText() {
List<String> hotText = new ArrayList<>();
if (this.getHotText() != null) {
this.getHotText().stream().limit(3).forEach((x) -> hotText.add(x.getText()));
}
return hotText;
}
/** Inserts a word into the trie. */
private void insert(String word) {
if (word != null) {
add(0, word, word.length());
}
}
private void add(int i, String word, int length) {
if (i < length) {
char c = word.charAt(i);
Trie subTrie = map.get(c);
if (subTrie == null) {
subTrie = new Trie();
map.put(c, subTrie);
}
subTrie.add(i + 1, word, length);
} else map.put(null, new Trie()); // use null to indicate end of string
}
/**
* Update hottex and degree
*
* @param word word or sentence
*/
private void update(String word) {
if (word != null) {
update(0, word, word.length());
}
}
/**
* Update trie
*
* @param i curr position
* @param word sentence
* @param length length
* @return HotText
*/
private HotText update(int i, String word, int length) {
if (i < length) {
char c = word.charAt(i);
Trie subTrie = map.get(c);
HotText subTrieHotText = subTrie.update(i + 1, word, length);
HotText currHotText =
new HotText(
c + (subTrieHotText == null ? "" : subTrieHotText.getText()), hotTextMap.get(word));
updateHotText(subTrie, currHotText);
return currHotText;
}
return null;
}
/**
* Hot text update
*
* @param hotText hotText object
*/
private void updateHotText(Trie trie, HotText hotText) {
trie.getHotText()
.remove(new HotText(hotText.getText(), hotText.getDegree() - 1)); // remove already
// contained hot-text and add new
trie.getHotText().add(hotText);
}
/**
* Contains child
*
* @param c char
* @return true if it contains child, false otherwise
*/
private boolean containsChild(char c) {
return this.map.containsKey(c);
}
/**
* Return child tree
*
* @param c char
* @return child subTrie
*/
private Trie getSubtrie(char c) {
return this.map.get(c);
}
}
}
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