题目：

题解：

type node struct {keys  map[string]struct{}count int
}type AllOne struct {*list.Listnodes 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 nodesdelete(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 ""
}