原文链接: https://leetcode-cn.com/problems/words-frequency-lcci

英文原文

Design a method to find the frequency of occurrences of any given word in a book. What if we were running this algorithm multiple times?

You should implement following methods:

• WordsFrequency(book) constructor, parameter is a array of strings, representing the book.
• get(word) get the frequency of word in the book. 

Example:

WordsFrequency wordsFrequency = new WordsFrequency({"i", "have", "an", "apple", "he", "have", "a", "pen"});
wordsFrequency.get("you"); //returns 0，"you" is not in the book
wordsFrequency.get("have"); //returns 2，"have" occurs twice in the book
wordsFrequency.get("an"); //returns 1
wordsFrequency.get("apple"); //returns 1
wordsFrequency.get("pen"); //returns 1

Note:

• There are only lowercase letters in book[i].
• 1 <= book.length <= 100000
• 1 <= book[i].length <= 10
• get function will not be called more than 100000 times.

中文题目

设计一个方法，找出任意指定单词在一本书中的出现频率。

你的实现应该支持如下操作：

• WordsFrequency(book)构造函数，参数为字符串数组构成的一本书
• get(word)查询指定单词在书中出现的频率

示例：

WordsFrequency wordsFrequency = new WordsFrequency({"i", "have", "an", "apple", "he", "have", "a", "pen"});
wordsFrequency.get("you"); //返回0，"you"没有出现过
wordsFrequency.get("have"); //返回2，"have"出现2次
wordsFrequency.get("an"); //返回1
wordsFrequency.get("apple"); //返回1
wordsFrequency.get("pen"); //返回1

提示：

• book[i]中只包含小写字母
• 1 <= book.length <= 100000
• 1 <= book[i].length <= 10
• get函数的调用次数不会超过100000

通过代码

高赞题解

class WordsFrequency {
    private HashMap<String, Integer> map = new HashMap<>();

    public WordsFrequency(String[] book) {
        for (String word : book) {
            map.put(word, map.getOrDefault(word, 0) + 1);
        }
    }

    public int get(String word) {
        return map.getOrDefault(word, 0);
    }
}

统计信息

通过次数	提交次数	AC比率
15759	20638	76.4%

提交历史

提交时间	提交结果	执行时间	内存消耗	语言