leetcode2671--频率跟踪器

1. 题意

设计一个频率跟踪器，查询出现的数字和出现的频率。

频率跟踪器

2. 题解

双哈希表，一个跟踪加入数字，一个跟踪频率。

• 代码

class FrequencyTracker {
    unordered_map<int,int> p;
    unordered_map<int,int> freq;
public:
    FrequencyTracker() {

    }
    
    void add(int number) {
        // p[number]++
        // freq[p[number]]++
        if (p.find(number) != p.end())
            freq[p[number]]--;
        p[number]++;
        freq[p[number]]++;
    }
    
    void deleteOne(int number) {
        
        // if p[number] > 0
        if ( p[number] > 0) {
            freq[p[number]]--;
            p[number]--;
            if ( p[number] > 0){
                freq[p[number]]++;
            }
        }
    }
    
    bool hasFrequency(int frequency) {
        // has freq and freq[f] > 0
        return freq.find(frequency) != freq.end() && freq[frequency] != 0;
    }
};

/**
 * Your FrequencyTracker object will be instantiated and called as such:
 * FrequencyTracker* obj = new FrequencyTracker();
 * obj->add(number);
 * obj->deleteOne(number);
 * bool param_3 = obj->hasFrequency(frequency);
 */
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