package reverse

func reverseStr(str string, specialChars string) string {
	dic := map[byte]bool{}
	for i := 0; i < len(specialChars); i++ {
		dic[specialChars[i]] = true
	}

	// assume all are ascii characters
	out := make([]byte, len(str))
	l, r := 0, len(str)-1
	for l <= r {

		if dic[str[l]] {
			out[l] = str[l]
			l++
		} else if dic[str[r]] {
			out[r] = str[r]
			r--
		} else {
			out[l], out[r] = str[r], str[l]
			l++
			r--
		}
	}

	return string(out)
}

/*
package reverse

import (
	"fmt"
	"sort"
	"testing"
)

func TestReverseArrayWithSpecialChars(t *testing.T) {
	specialChars := ",!$"
	cases := []struct {
		in   string
		want string
	}{
		{in: "Ab,c,de!$", want: "ed,c,bA!$"},
		{in: "a,b$c", want: "c,b$a"},
	}

	for i, tc := range cases {
		out := reverseStr(tc.in, specialChars)
		if tc.want != out {
			t.Errorf("case %d, want %s, got %s", i, tc.want, out)
		}

	}

}

func TestSortOrder(t *testing.T) {
	ints := []int{1, 10, 21, 2}

	sort.Slice(ints, func(i, j int) bool {
		return ints[i] > ints[j]
	})

	fmt.Printf("%+v\n", ints) // output for debug

}
*/