1730D - Prefixes and Suffixes - CodeForces Solution

def putin():
    return map(int, input().split())


def solve():
    n = int(input())
    s = input()
    r = input()
    pairs = []
    for i in range(len(s)):
        pairs.append(
            tuple(sorted([s[i], r[n-1-i]]))
        )
    D = {}
    for elem in pairs:
        if elem in D:
            D[elem] += 1
        else:
            D[elem] = 1
    odd = 0
    for elem in D:
        if D[elem] % 2 == 1:
            if elem[0] != elem[1]:
                return "NO"
            odd += 1
    return "YES" if odd < 2 else "NO"



t = int(input())
for i in range(t):
    print(solve())