Solution.go

type Trie struct {
	children [26]*Trie
	v        int
	pv       int
}

func Constructor() (_ Trie) { return }

func (this *Trie) Insert(word string) {
	node := this
	for _, c := range word {
		c -= 'a'
		if node.children[c] == nil {
			node.children[c] = &Trie{}
		}
		node = node.children[c]
		node.pv++
	}
	node.v++
}

func (this *Trie) CountWordsEqualTo(word string) int {
	node := this.search(word)
	if node == nil {
		return 0
	}
	return node.v
}

func (this *Trie) CountWordsStartingWith(prefix string) int {
	node := this.search(prefix)
	if node == nil {
		return 0
	}
	return node.pv
}

func (this *Trie) Erase(word string) {
	node := this
	for _, c := range word {
		c -= 'a'
		node = node.children[c]
		node.pv--
	}
	node.v--
}

func (this *Trie) search(word string) *Trie {
	node := this
	for _, c := range word {
		c -= 'a'
		if node.children[c] == nil {
			return nil
		}
		node = node.children[c]
	}
	return node
}

/**
 * Your Trie object will be instantiated and called as such:
 * obj := Constructor();
 * obj.Insert(word);
 * param_2 := obj.CountWordsEqualTo(word);
 * param_3 := obj.CountWordsStartingWith(prefix);
 * obj.Erase(word);
 */