first_non_repeated.go

package main

import "fmt"
import "log"
import "bufio"
import "os"
import "strings"

type RunePosCount struct {
	Pos, Count int
}

func getFirst(in string) string {
	nonRepeated := make(map[rune]RunePosCount, len(in))
	for ix, char := range in {
		val, ok := nonRepeated[char]
		if !ok {
			nonRepeated[char] = RunePosCount{ix, 1}
		} else {
			nonRepeated[char] = RunePosCount{val.Pos, val.Count + 1}
			//fmt.Println(string(char), ix, val.Count + 1)
		}
	}

	//fmt.Println(nonRepeated)
	lowestPos := len(in)
	out := rune(0)
	for char, posCount := range nonRepeated {
		if posCount.Count == 1 && posCount.Pos < lowestPos {
			out = char
			lowestPos = posCount.Pos
		}
	}
	return string(out)
}

func main() {
	file, err := os.Open(os.Args[1])
	if err != nil {
		log.Fatal(err)
	}
	defer file.Close()
	scanner := bufio.NewScanner(file)
	for scanner.Scan() {
		line := strings.TrimSpace(scanner.Text())
		fmt.Println(getFirst(line))
	}
}