main.go

package main

import (
	"bytes"
	"fmt"
	"strconv"
	"strings"
)

func comma(s string) string {
	n := len(s)
	if n <= 3 {
		return s
	}
	return comma(s[:n-3]) + "," + s[n-3:]
}
func intsToString(values []int) string {

	var buf bytes.Buffer

	buf.WriteByte('[')

	for i, v := range values {
		if i > 0 {
			buf.WriteString(", ")
		}
		fmt.Fprintf(&buf, "%d", v)
	}

	buf.WriteByte(']')

	return buf.String()
}

func main() {
	fmt.Println(intsToString([]int{1, 2, 3})) // "[1, 2, 3]"
}

//SOLUTION 3.10 : INSERT COMMAS INTO BYTE
func insertCommas(str string) string {
	x := &bytes.Buffer{}
	prev := len(str) % 3

	if prev == 0 {
		prev = 3
	}
	x.WriteString(str[:prev])

	for i := prev; i < len(str); i += 3 {
		x.WriteByte(',')
		x.WriteString(str[i : i+3])
	}
	return x.String()
}

func basename(s string) string {
	slash := strings.LastIndex(s, "/") // -1 if "/" not found

	s = s[slash+1:]

	if dot := strings.LastIndex(s, "."); dot >= 0 {
		s = s[:dot]
	}

	return s
}

func basename2(s string) string {
	// Discard last '/' and everything before.
	for i := len(s) - 1; i >= 0; i-- {
		if s[i] == '/' {
			s = s[i+1:]
			break
		}
	}
	// Preserve everything before last '.'.
	for i := len(s) - 1; i >= 0; i-- {
		if s[i] == '.' {
			s = s[:i]
			break
		}
	}
	return s
}

//3.11 SOLUTION: String format

func Format(n int64) string {
	in := strconv.FormatInt(n, 10)
	numOfDigits := len(in)
	if n < 0 {
		numOfDigits-- // First character is the - sign (not a digit)
	}
	numOfCommas := (numOfDigits - 1) / 3

	out := make([]byte, len(in)+numOfCommas)
	if n < 0 {
		in, out[0] = in[1:], '-'
	}

	for i, j, k := len(in)-1, len(out)-1, 0; ; i, j = i-1, j-1 {
		out[j] = in[i]
		if i == 0 {
			return string(out)
		}
		if k++; k == 3 {
			j, k = j-1, 0
			out[j] = ','
		}
	}
}

//SOLUTION 3.12 and 3.13 : is Anagram or not
func isAnagram(s string, t string) bool {

	lenS := len(s)
	lenT := len(t)

	if lenS != lenT {
		return false
	}

	anagramMap := make(map[string]int)

	for i := 0; i < lenS; i++ {
		anagramMap[string(s[i])]++
	}

	for i := 0; i < lenT; i++ {
		anagramMap[string(t[i])]--
	}

	for i := 0; i < lenS; i++ {
		if anagramMap[string(s[i])] != 0 {
			return false
		}
	}

	return true
}