leetcode 1315.祖父结点值为偶数的和

1.题目要求:

2.题目实列:

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

3.做题步骤:
巧妙运用map容器求次数
4.题目代码:

class WordsFrequency {
public:
    //使用map容器，把每个单词的频率统计出来
    map<string,int> word_count;
    WordsFrequency(vector<string>& book) {
        for(int i = 0;i < book.size();i++){
            map<string,int> :: iterator it = word_count.find(book[i]);
            if(it != word_count.end()){
                it->second += 1;
            }else{
                word_count.insert(make_pair(book[i],1));
            }
        }
    }
    
    int get(string word) {
        //返回单词频率
        map<string,int> :: iterator it = word_count.find(word);
        if(it != word_count.end()){
            return it->second;
        }else{
            return 0;
        }
    }
};

/**
 * Your WordsFrequency object will be instantiated and called as such:
 * WordsFrequency* obj = new WordsFrequency(book);
 * int param_1 = obj->get(word);
 */