package main

func LongestDupSubstringBruteforce(s string) string {
	strLen := len(s)
	if strLen < 2 {
		return ""
	}

	res := ""
	for ln := 1; ln < strLen; ln++ {
		for i := 0; i <= strLen-ln; i++ {
			word1 := s[i : i+ln]
			count := 0
			for j := 0; j <= strLen-ln; j++ {
				word2 := s[j : j+ln]
				if word1 == word2 {
					count++
					if count > 1 {
						res = word1
						break
					}
				}
			}
		}
	}

	return res
}

func LongestDupSubstringReversedBruteforce(s string) string {
	strLen := len(s)
	if strLen < 2 {
		return ""
	}

	for ln := strLen - 1; ln >= 1; ln-- {
		for i := strLen - ln; i >= 0; i-- {
			word1 := s[i : i+ln]
			count := 0
			for j := strLen - ln; j >= 0; j-- {
				word2 := s[j : j+ln]
				if word1 == word2 {
					count++
					if count > 1 {
						return word1
					}
				}
			}
		}
	}

	return ""
}

func LongestDupSubstringSmartforce(s string) string {
	strLen := len(s)
	if strLen < 2 {
		return ""
	}

	indicesCurrent := []int{}
	indicesNext := []int{}

	res := ""
	for i := 0; i < strLen; i++ {

		for j := 0; j < strLen; j++ {
			indicesCurrent = append(indicesCurrent, j)
		}

		for ln := 1; ln <= strLen-i; ln++ {
			word1 := s[i : i+ln]

			for _, index := range indicesCurrent {
				if index+ln > strLen {
					continue
				}
				word2 := s[index : index+ln]
				if (word1 == word2) && (index != i) {

					if len(res) < len(word1) {
						res = word1
					}
					indicesNext = append(indicesNext, index)
				}
			}

			indicesCurrent = indicesNext
			indicesNext = []int{}
		}
	}

	return res
}

func LongestDupSubstring(s string) string {
	return LongestDupSubstringSmartforce(s)
}