Search Suggestions System (M)

题目

Given an array of strings products and a string searchWord. We want to design a system that suggests at most three product names from products after each character of searchWord is typed. Suggested products should have common prefix with the searchWord. If there are more than three products with a common prefix return the three lexicographically minimums products.

Return list of lists of the suggested products after each character of searchWord is typed.

Example 1:

Input: products = ["mobile","mouse","moneypot","monitor","mousepad"], searchWord = "mouse"
Output: [
["mobile","moneypot","monitor"],
["mobile","moneypot","monitor"],
["mouse","mousepad"],
["mouse","mousepad"],
["mouse","mousepad"]
]
Explanation: products sorted lexicographically = ["mobile","moneypot","monitor","mouse","mousepad"]
After typing m and mo all products match and we show user ["mobile","moneypot","monitor"]
After typing mou, mous and mouse the system suggests ["mouse","mousepad"]

Example 2:

Input: products = ["havana"], searchWord = "havana"
Output: [["havana"],["havana"],["havana"],["havana"],["havana"],["havana"]]

Example 3:

Input: products = ["bags","baggage","banner","box","cloths"], searchWord = "bags"
Output: [["baggage","bags","banner"],["baggage","bags","banner"],["baggage","bags"],["bags"]]

Example 4:

Input: products = ["havana"], searchWord = "tatiana"
Output: [[],[],[],[],[],[],[]]

Constraints:

• 1 <= products.length <= 1000
• There are no repeated elements in products.
• 1 <= Σ products[i].length <= 2 * 10^4
• All characters of products[i] are lower-case English letters.
• 1 <= searchWord.length <= 1000
• All characters of searchWord are lower-case English letters.

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题意

实现一个搜索提示功能：每输入一个字符，返回三个以已经输入的字符作为前缀的单词字符串。

思路

字典树。先构建字典树，再遍历searchWord的每一个前缀，找到最多3个符合的单词。

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代码实现

Java

class Solution {
    public List<List<String>> suggestedProducts(String[] products, String searchWord) {
        List<List<String>> ans = new ArrayList<>();
        Trie root = new Trie();
        
        for (int i =0 ; i < products.length;i++) {
            insert(root, products[i], i);
        }

        for (char c : searchWord.toCharArray()) {
            List<String> tmp = new ArrayList<>();
            if (root == null || root.children[c - 'a'] == null) {
                root = null;
            } else {
                root = root.children[c - 'a'];
                find(root, products, tmp);
            }
            ans.add(tmp);
        }

        return ans;
    }

    private void find(Trie root, String[] products, List<String> list) {
        if (list.size() == 3) return;
        if (root.isEnd) list.add(products[root.index]);

        for (int i = 0; i < 26; i++) {
            if (root.children[i] != null) {
                find(root.children[i], products, list);
            }
        }
    }

    private void insert(Trie root, String word, int index) {
        for (char c : word.toCharArray()) {
            if (root.children[c - 'a'] == null) root.children[c - 'a'] = new Trie();
            root = root.children[c - 'a'];
        }
        root.isEnd = true;
        root.index = index;
    }

    class Trie {
        Trie[] children = new Trie[26];
        boolean isEnd = false;
        int index;
    }
}

JavaScript

/**
 * @param {string[]} products
 * @param {string} searchWord
 * @return {string[][]}
 */
var suggestedProducts = function (products, searchWord) {
    const ans = []
    
    for (let i = 1; i <= searchWord.length; i++) {
        const remain = products.filter(word => word.startsWith(searchWord.slice(0, i)))
        ans.push(remain.sort().slice(0, 3))
    }
    
    return ans
}