package main

import (
	"bufio"
	"fmt"
	"os"
)

func main() {
	in := bufio.NewReader(os.Stdin)
	out := bufio.NewWriter(os.Stdout)
	defer out.Flush()

	var q int
	fmt.Fscan(in, &q)

	for i := 0; i < q; i++ {
		var n int
		fmt.Fscan(in, &n)
		var s, t string
		fmt.Fscan(in, &s, &t)

		var countS, countT [26]int
		for j := 0; j < n; j++ {
			countS[s[j]-'a']++
			countT[t[j]-'a']++
		}

		possible := true
		for j := 0; j < 26; j++ {
			if countS[j] != countT[j] {
				possible = false
				break
			}
		}

		if !possible {
			fmt.Fprintln(out, "NO")
			continue
		}

		hasDuplicate := false
		for j := 0; j < 26; j++ {
			if countS[j] > 1 {
				hasDuplicate = true
				break
			}
		}

		if hasDuplicate {
			fmt.Fprintln(out, "YES")
		} else {
			invS := 0
			for j := 0; j < n; j++ {
				for k := j + 1; k < n; k++ {
					if s[j] > s[k] {
						invS++
					}
				}
			}
			invT := 0
			for j := 0; j < n; j++ {
				for k := j + 1; k < n; k++ {
					if t[j] > t[k] {
						invT++
					}
				}
			}
			if invS%2 == invT%2 {
				fmt.Fprintln(out, "YES")
			} else {
				fmt.Fprintln(out, "NO")
			}
		}
	}
}