最近请求次数(TreeMap应用)

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mob604756e605af 2021-08-29 16:19:00

最近请求次数(TreeMap应用)_java

这是我的废物写法

class RecentCounter {
    Deque<Integer> sta;
    public RecentCounter() {
        this.sta = new LinkedList<>(); 
    }
    
    public int ping(int t) {
        int res = 1;
        Deque<Integer> test = new LinkedList<>();
        while(!sta.isEmpty() && sta.peekLast() >= t-3000){
            test.addLast(sta.pollLast());
            res++;
        }
        while(!test.isEmpty()){
            sta.addLast(test.pollLast());
        }
        sta.addLast(t);
        return res;
    }
}

/**
 * Your RecentCounter object will be instantiated and called as such:
 * RecentCounter obj = new RecentCounter();
 * int param_1 = obj.ping(t);
 */

这是应用TreeMap

java中的TreeMap是一类有序集合，能够快速返回一个特定大小的值，例如下面用到的ceilingKey，就是返回TreeMap中第一个大于等于t-3000的值，类似的函数还有floor等，用起来很方便

class RecentCounter {

    TreeMap<Integer, Integer> tm;
    List<Integer> record;
    
    public RecentCounter() {
        tm = new TreeMap<>();
        record = new ArrayList<>();
    }

    public int ping(int t) {
        tm.put(t, record.size());
        record.add(t);
        Integer target = tm.ceilingKey(t - 3000);
        return record.size() - tm.get(target);
    }
}