package main

type StringMap struct {
	Map SubStringMap
}

func NewStringMap() *StringMap {
	return &StringMap{
		Map: map[byte]*StringMap{},
	}
}

func (sm *StringMap) CombineAllSubStrings(prefix string, rev bool) []string {
	if len(sm.Map) == 0 {
		return []string{prefix}
	}
	out := []string{}
	for chr, Map := range sm.Map {
		if rev {
			out = append(out, Map.CombineAllSubStrings(string(chr)+prefix, rev)...)
		} else {
			out = append(out, Map.CombineAllSubStrings(prefix+string(chr), rev)...)
		}
	}
	return out
}

func (sm *StringMap) Add(word string, rev bool) {
	if len(word) == 0 {
		return
	}
	take := 0
	if rev {
		take = len(word) - 1
	}
	sub, ok := sm.Map[word[take]]
	if !ok {
		sub = NewStringMap()
		sm.Map[word[take]] = sub
	}
	if rev {
		sub.Add(word[:take], rev)
	} else {
		sub.Add(word[1:], rev)
	}
}

type SubStringMap = map[byte]*StringMap

type WordFilter struct {
	Prefixes *StringMap
	Suffixes *StringMap
	Words    map[string]int
}

func Constructor(words []string) WordFilter {
	Prefixes := NewStringMap()
	Suffixes := NewStringMap()
	Words := map[string]int{}

	for idx, word := range words {
		Words[word] = idx
		Prefixes.Add(word, false)
		Suffixes.Add(word, true)
	}
	return WordFilter{
		Prefixes: Prefixes,
		Suffixes: Suffixes,
		Words:    Words,
	}
}

func (wf *WordFilter) F(prefix, suffix string) int {
	prefix_base, ok := wf.Prefixes, true
	for i := range prefix {
		prefix_base, ok = prefix_base.Map[prefix[i]]
		if !ok {
			return -1
		}
	}
	suffix_base := wf.Suffixes
	for i := len(suffix) - 1; i >= 0; i-- {
		suffix_base, ok = suffix_base.Map[suffix[i]]
		if !ok {
			return -1
		}
	}
	prefix_found := map[string]bool{}
	for _, found := range prefix_base.CombineAllSubStrings(prefix, false) {
		prefix_found[found] = true
	}

	max := -1
	for _, found := range suffix_base.CombineAllSubStrings(suffix, true) {
		if _, ok := prefix_found[found]; ok {
			idx := wf.Words[found]
			if idx > max {
				max = idx
			}
		}
	}
	return max
}

/**
 * Your WordFilter object will be instantiated and called as such:
 * obj := Constructor(words);
 * param_1 := obj.F(prefix,suffix);
 */