t = int(input()) for _ in range(t): ret = 'YES' n, k = list(map(int, input().split(' '))) s = input() t = input() for i in range(max(n - k, 0), min(k, n)): if s[i] != t[i]: ret = 'NO' if sorted(s) != sorted(t): ret = 'NO' print(ret)
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