关于算法:LC-2034-Stock-Price-Fluctuation

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class StockPrice {
    // key: time, value: price
    private Map<Integer, Integer> timePrice;
    // key: price, value: frequency，应用tree map，使得依照price从小到大排序，不便间接获取max / min
    private TreeMap<Integer, Integer> priceFreq;
    private int latestTime; // 最新的工夫

    public StockPrice() {
        timePrice = new HashMap<>();
        latestTime = 0;
        priceFreq = new TreeMap<>();
    }

    public void update(int timestamp, int price) {
        // 更新最新工夫，始终让latestTime放弃为最近的工夫戳，在调用current办法时，间接从map中获取
        latestTime = Math.max(latestTime, timestamp);
        // 如果工夫戳之前保留过，那么对频率表进行更新
        if (timePrice.containsKey(timestamp)) {
            // 依据工夫戳，拿到之前的旧price
            int oldPrice = timePrice.get(timestamp);
            // 因为更改了，所以把频率-1
            priceFreq.put(oldPrice, priceFreq.get(oldPrice) - 1);
            // 如果该price频率更改后为0，那么须要移除该price
            if (priceFreq.get(oldPrice) == 0) priceFreq.remove(oldPrice);
        }
        // 别离更新两个map中的新的price
        timePrice.put(timestamp, price);
        priceFreq.put(price, priceFreq.getOrDefault(price, 0) + 1);
    }

    public int current() {
        // 依据最新工夫间接获取price
        return timePrice.get(latestTime);
    }

    public int maximum() {
        // 从priceFreq中间接取最初那个最大price
        return priceFreq.lastKey();
    }

    public int minimum() {
        // 从priceFreq中间接取第一个最小的price
        return priceFreq.firstKey();
    }
}