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// @Title: 全 O(1) 的数据结构 (All O`one Data Structure)
// @Author: 15816537946@163.com
// @Date: 2022-03-16 16:47:49
// @Runtime: 96 ms
// @Memory: 17.8 MB
import (
	"container/list"
)

// LFU
type node struct {
	keys  map[string]struct{}
	count int
}

type AllOne struct {
	*list.List
	nodes map[string]*list.Element
}

func Constructor() AllOne {
	return AllOne{list.New(), map[string]*list.Element{}}
}

func (l *AllOne) Inc(key string) {
	if cur := l.nodes[key]; cur != nil {
		curNode := cur.Value.(node)
		if nxt := cur.Next(); nxt == nil || nxt.Value.(node).count > curNode.count+1 {
			l.nodes[key] = l.InsertAfter(node{map[string]struct{}{key: {}}, curNode.count + 1}, cur)
		} else {
			nxt.Value.(node).keys[key] = struct{}{}
			l.nodes[key] = nxt
		}

		delete(curNode.keys, key)
		if len(curNode.keys) == 0 {
			l.Remove(cur)
		}
	} else {
		// key 不在链表中
		if l.Front() == nil || l.Front().Value.(node).count > 1 {
			l.nodes[key] = l.PushFront(node{map[string]struct{}{key: {}}, 1})
		} else {
			l.Front().Value.(node).keys[key] = struct{}{}
			l.nodes[key] = l.Front()
		}
	}
}

func (l *AllOne) Dec(key string) {
	cur := l.nodes[key]
	curNode := cur.Value.(node)
	if curNode.count > 1 {
		if pre := cur.Prev(); pre == nil || pre.Value.(node).count < curNode.count-1 {
			l.nodes[key] = l.InsertBefore(node{map[string]struct{}{key: {}}, curNode.count - 1}, cur)
		} else {
			pre.Value.(node).keys[key] = struct{}{}
			l.nodes[key] = pre
		}
	} else {
		// key 仅出现一次，将其移出 nodes
		delete(l.nodes, key)
	}
	delete(curNode.keys, key)
	if len(curNode.keys) == 0 {
		l.Remove(cur)
	}
}

func (l *AllOne) GetMaxKey() string {
	if b := l.Back(); b != nil {
		for key := range b.Value.(node).keys {
			return key
		}
	}
	return ""
}

func (l *AllOne) GetMinKey() string {
	if f := l.Front(); f != nil {
		for key := range f.Value.(node).keys {
			return key
		}
	}
	return ""
}