leetcode-go/hard/432.all-oone-data-structure.go

type none struct{}

type pair struct {
	key int
	set map[string]none
}

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

/** Initialize your data structure here. */
func Constructor() AllOne {
	return AllOne{
		m:  make(map[string]*list.Element),
		li: list.New(),
	}
}

/** Inserts a new key <Key> with value 1. Or increments an existing key by 1. */
func (this *AllOne) Inc(key string) {
	if val, ok := this.m[key]; ok { // Increments
		next := val.Next()
		if next == nil || val.Value.(pair).key+1 < next.Value.(pair).key { // Insert after
			next = this.li.InsertAfter(pair{val.Value.(pair).key + 1, map[string]none{key: none{}}}, val)
		} else { // Increment after
			next.Value.(pair).set[key] = none{}
		}
		this.m[key] = next
		if len(val.Value.(pair).set) == 1 { // Remove current element
			this.li.Remove(val)
		} else { // Remove from set
			delete(val.Value.(pair).set, key)
		}
	} else { // Inserts
		if this.li.Len() == 0 || 1 < this.li.Front().Value.(pair).key { // Push front
			this.li.PushFront(pair{1, map[string]none{key: none{}}})
		} else { // Move to ones set
			this.li.Front().Value.(pair).set[key] = none{}
		}
		this.m[key] = this.li.Front()
	}
}

/** Decrements an existing key by 1. If Key's value is 1, remove it from the data structure. */
func (this *AllOne) Dec(key string) {
	if val, ok := this.m[key]; ok {
		if val.Value.(pair).key == 1 { // Removes
			if len(val.Value.(pair).set) == 1 { // Remove whole element
				this.li.Remove(val)
			} else { // Remove from set
				delete(val.Value.(pair).set, key)
			}
			delete(this.m, key) // Remove from map
		} else { // Decrements
			prev := val.Prev()
			if prev == nil || prev.Value.(pair).key < val.Value.(pair).key-1 { // Insert before
				prev = this.li.InsertBefore(pair{val.Value.(pair).key - 1, map[string]none{key: none{}}}, val)
			} else { // Move to prev set
				prev.Value.(pair).set[key] = none{}
			}
			this.m[key] = prev
			if len(val.Value.(pair).set) == 1 { // Remove current element
				this.li.Remove(val)
			} else {
				delete(val.Value.(pair).set, key) // Remove from set
			}
		}
	}
}

/** Returns one of the keys with maximal value. */
func (this *AllOne) GetMaxKey() string {
	if this.li.Len() != 0 {
		set := this.li.Back().Value.(pair).set
		for k := range set {
			return k
		}
	}
	return ""
}

/** Returns one of the keys with Minimal value. */
func (this *AllOne) GetMinKey() string {
	if this.li.Len() != 0 {
		set := this.li.Front().Value.(pair).set
		for k := range set {
			return k
		}
	}
	return ""
}

/**
 * Your AllOne object will be instantiated and called as such:
 * obj := Constructor();
 * obj.Inc(key);
 * obj.Dec(key);
 * param_3 := obj.GetMaxKey();
 * param_4 := obj.GetMinKey();
 */