1268. Search Suggestions System

I user Trie to store the products. For every Trie node, it has the links to the next character and a PriorityQueue. 

The PriorityQueue is used to store all products has has a prefix till the node's character.

After the Trie is build up, the searching will be very easy.

The Time Complexity:

Insert: O(n), n is the total number of characters in products.

Search: O(m*klog(k)), m is the length of SearchWord, k is the number of String in PriorityQueue.

Space Complexity: O(26*n) = O(n), n is the total number of characters in products.

 

class Solution {
    class Trie{
        Trie[] next = new Trie[26];
        PriorityQueue<String> products = new PriorityQueue<>();
        
        public void insert(String s){
            Trie t = this;
            for(char c: s.toCharArray()){
                if(t.next[c-'a']==null)
                    t.next[c-'a']= new Trie();
                t = t.next[c-'a'];
                t.products.offer(s);
            }
        }
        
        public List<List<String>> search(String s){
            List<List<String>> res = new ArrayList<>();
            Trie t = this;
            for(char c: s.toCharArray()){
                if(t!=null){
                    t = t.next[c-'a'];
                    if(t!=null){
                        int size = Math.min(3, t.products.size());
                        List<String> list = new ArrayList<>();
                        for(int i=0;i<size;i++){
                            list.add(t.products.poll());
                        }
                        res.add(list);
                    }else{
                        res.add(new ArrayList<>());
                    }
                }else
                    res.add(new ArrayList<>());
            }
            return res;
        }
    }
    public List<List<String>> suggestedProducts(String[] products, String searchWord) {
        Trie t = new Trie();
        for(String s: products){
            t.insert(s);
        }
        return t.search(searchWord);
    }
}