package main
// Return the longest substring of an input string without repeated
// characters.  See longunstr.py for more context.

import (
	"fmt"
	"os"
)

func Longunstr(s string) string {
	r := []rune(s)
	var i, n, m int
	p := make(map[rune]int)
	
	for j, c := range r {
		q, ok := p[c]
		if ok && q >= i {
			// advance past last match
			i = q + 1
		}

		p[c] = j

		// longer?
		if j+1 - i > m - n {
			n = i
			m = j+1
		}
	}

	return string(r[n:m])
}

// Same result, but easier to explain, and much slower
func Longunstr_basic(s string) string {
	r := ([]rune)(s)
	var n, m int
	for i := range r {
		seen := make(map[rune]bool)

		for j := i; j < len(r); j++ {
			jc := r[j]
			if seen[jc] {
				break
			}
			seen[jc] = true

			if j+1 - i > m - n {
				n = i
				m = j + 1
			}
		}
	}

	return (string)(r[n:m])
}
			

func main() {
	fmt.Println(Longunstr_basic(os.Args[1]), Longunstr(os.Args[1]))
}