main.go

package main

import (
	"fmt"
	"math/big"
	"modernc.org/sortutil"
	"sort"
)

func hasUniqueCharacters1(str string) (string, bool) {
	for i := 0; i < len(str); i++ {
		for j := i + 1; j < len(str); j++ {
			if str[i] == str[j] {
				return str, false
			}
		}
	}
	return str, true
}

func hasUniqueCharacters2(str string) (string, bool) {
	chars := []rune(str)
	length := len(chars)
	for i := 0; i < length; i++ {
		for j := i + 1; j < length; j++ {
			if chars[j] == chars[i] {
				return str, false
			}
		}
	}
	return str, true
}

func hasUniqueCharacters3(str string) (string, bool) {
	chars := sortutil.RuneSlice(str)
	length := len(chars)
	sort.Sort(chars)

	for i := 0; i < length-1; i++ {
		if chars[i] == chars[i+1] {
			return str, false
		}
		continue
	}
	return str, true
}

func hasUniqueCharacters4(str string) (string, bool) {
	chars := []rune(str)
	length := len(chars)
	sort.Slice(chars, func(i int, j int) bool {
		return chars[i] < chars[j]
	})
	for i := 0; i < length-1; i++ {
		if chars[i] == chars[i+1] {
			return str, false
		}
		continue
	}
	return str, true
}

func hasUniqueCharacters5(str string) (string, bool) {
	var bits big.Int
	for _, char := range str {
		val := int(char)
		if bits.Bit(val) != 0 {
			return str, false
		}
		bits.SetBit(&bits, val, 1)
	}
	return str, true
}

func hasUniqueCharacters6(str string) (string, bool) {
	var bits = make(map[int]bool, len(str))
	for _, char := range str {
		val := int(char)
		if bits[val] {
			return str, false
		}
		bits[val] = true
	}
	return str, true
}

const MAX_CHAR = 256
func hasUniqueCharacters7(str string) (string, bool) {
	if len(str) > MAX_CHAR {
		return str, false
	}

	chars := make([]bool, MAX_CHAR)
	for _, char := range str {
		val := int(char)
		if chars[val] {
			return str, false
		}
		chars[val] = true
	}
	return str, true
}

func hasUniqueCharacters8(str string) (string, bool) {
	checker := 0
	for _, char := range str {
		index := char - 'a'
		val := 1 << index
		if checker&val > 0 {
			return str, false
		}
		checker |= val
	}
	return str, true
}