golang zipper

backwards.go

package main

import (
	"io"
	"io/ioutil"
	"os"
	"strings"
)

func main() {
	r := strings.NewReader(`-150`)
	if err := backwards(r, os.Stdout); err != nil {
		panic(err)
	}
}

const (
	Minus = `-`
	Zero  = `0`
)

func backwards(in io.Reader, out io.Writer) error {
	input, err := ioutil.ReadAll(in)
	if err != nil {
		return err
	}

	var (
		collection []string
	)

	for i, symbol := range strings.TrimSpace(string(input)) {
		if i == 0 && string(symbol) == Minus {
			_, _ = out.Write([]byte(Minus))
			continue
		}

		collection = append(collection, string(symbol))
	}

	startWriteValue := false
	for i := len(collection) - 1; i >= 0; i-- {
		if collection[i] == Zero && !startWriteValue {
			continue
		}

		_, _ = out.Write([]byte(collection[i]))
		if !startWriteValue {
			startWriteValue = true
		}

	}

	return nil
}

miss_ids.go

package main

import (
	"fmt"
	"io"
	"io/ioutil"
	"os"
	"strconv"
	"strings"
)

func main() {
	r := strings.NewReader(`7
6 4 1 2 3`)
	if err := missIDs(r, os.Stdout, 2); err != nil {
		panic(err)
	}
}

func missIDs(in io.Reader, out io.Writer, expectedMissCount int) error {
	input, err := ioutil.ReadAll(in)
	if err != nil {
		return err
	}

	inputs := strings.Split(string(input), "\n")

	if len(inputs) < 2 {
		return fmt.Errorf("expected 2 inputes rows, got - %d", len(inputs))
	}

	countAll, err := strconv.Atoi(inputs[0])
	if err != nil {
		return err
	}

	gotIDs := strings.Split(inputs[1], " ")
	if len(gotIDs) != countAll-2 {
		return fmt.Errorf("expected %d len of  row, got - %d", countAll-expectedMissCount, len(gotIDs))
	}

	index := make(map[string]bool, countAll)
	for _, id := range gotIDs {
		index[id] = true
	}

	var match int
	for i := 1; i <= countAll; i++ {
		if ok := index[strconv.Itoa(i)]; !ok {
			msg := strconv.Itoa(i)
			if match > 0 {
				msg = " " + msg
			}
			_, _ = out.Write([]byte(msg))
			match++
			if match == expectedMissCount {
				break
			}
		}
	}

	return nil
}

zipper.go

package main

import (
	"fmt"
	"io"
	"io/ioutil"
	"os"
	"strconv"
	"strings"
)

func main() {
	if err := zipper(os.Stdin, os.Stdout); err != nil {
		panic(err)
	}
}

func zipper(in io.Reader, out io.Writer) error {
	input, err := ioutil.ReadAll(in)
	if err != nil {
		return err
	}

	inputs := strings.Split(string(input), "\n")

	if len(inputs) < 3 {
		return fmt.Errorf("expected 3 inputes rows, got - %d", len(inputs))
	}

	lenOfRange, err := strconv.Atoi(inputs[0])
	if err != nil {
		return err
	}

	firstRange := strings.Split(inputs[1], " ")
	if len(firstRange) != lenOfRange {
		return fmt.Errorf("expected %d len of first row, got - %d", lenOfRange, len(firstRange))
	}

	secondRange := strings.Split(inputs[2], " ")

	if len(secondRange) != lenOfRange {
		return fmt.Errorf("expected %d len of second row, got - %d", lenOfRange, len(secondRange))
	}

	delimetr := []byte(` `)

	for i := 0; i < lenOfRange; i++ {
		if i != 0 {
			_, _ = out.Write(delimetr)
		}

		_, _ = out.Write([]byte(firstRange[i] + " " + secondRange[i]))
	}

	return nil
}