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CF1617A.Forbidden Subsequence
Forbidden Subsequence
You are given strings and , consisting of lowercase English letters. It is guaranteed that is a permutation of the string abc.
Find string , the lexicographically smallest permutation of such that is not a subsequence of .
String is a permutation of string if the number of occurrences of each distinct character is the same in both strings.
A string is a subsequence of a string if can be obtained from by deletion of several (possibly, zero or all) elements.
A string is lexicographically smaller than a string if and only if one of the following holds:
- is a prefix of , but ;
- in the first position where and differ, the string has a letter that appears earlier in the alphabet than the corresponding letter in .
Input
Each test contains multiple test cases. The first line contains a single integer () — the number of test cases. Description of the test cases follows.
The first line of each test case contains a string (), consisting of lowercase English letters.
The second line of each test case contains a string that is a permutation of the string abc. (Hence, ).
Note that there is no limit on the sum of across all test cases.
Output
For each test case, output a single string , the lexicographically smallest permutation of such that is not a subsequence of .
Note
In the first test case, both aaaabbc and aaaabcb are lexicographically smaller than aaaacbb, but they contain abc as a subsequence.
In the second test case, abccc is the smallest permutation of cccba and does not contain acb as a subsequence.
In the third test case, bcdis is the smallest permutation of dbsic and does not contain bac as a subsequence.
Samples
7
abacaba
abc
cccba
acb
dbsic
bac
abracadabra
abc
dddddddddddd
cba
bbc
abc
ac
abc
aaaacbb
abccc
bcdis
aaaaacbbdrr
dddddddddddd
bbc
ac
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