LeetCode : 895. Maximum Frequency Stack

class FreqStack {
    class Item {
        int index, value, freq;
        Item(int value, int index, int freq) {
            this.value = value;
            this.index = index;
            this.freq = freq;
        }
    }

    int index;
    PriorityQueue<Item> pq;
    Map<Integer, Integer> map;

    public FreqStack() {
        map = new HashMap();
        pq = new PriorityQueue<>((a,b) -> (a.freq == b.freq) ?
                                 b.index - a.index: b.freq - a.freq);
        index = 0;
    }

    public void push(int x) {
        map.merge(x, 1, Integer::sum);
        pq.add(new Item(x, index++, map.get(x)));
    }

    public int pop() {
        int value = pq.remove().value;
        map.merge(value, -1, Integer::sum);
        return value;
    }
}

/**
 * Your FreqStack object will be instantiated and called as such:
 * FreqStack obj = new FreqStack();
 * obj.push(x);
 * int param_2 = obj.pop();
 */
congr / world

LeetCode : 895. Maximum Frequency Stack #466
