Codeforces Round 726 (Div. 2) |
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Finished |
This is the easy version of the problem. The only difference is the constraints on $$$n$$$ and $$$k$$$. You can make hacks only if all versions of the problem are solved.
You have a string $$$s$$$, and you can do two types of operations on it:
You can use each operation any number of times (possibly none).
Your task is to find the lexicographically smallest string of length exactly $$$k$$$ that can be obtained by doing these operations on string $$$s$$$.
A string $$$a$$$ is lexicographically smaller than a string $$$b$$$ if and only if one of the following holds:
The first line contains two integers $$$n$$$, $$$k$$$ ($$$1 \leq n, k \leq 5000$$$) — the length of the original string $$$s$$$ and the length of the desired string.
The second line contains the string $$$s$$$, consisting of $$$n$$$ lowercase English letters.
Print the lexicographically smallest string of length $$$k$$$ that can be obtained by doing the operations on string $$$s$$$.
8 16 dbcadabc
dbcadabcdbcadabc
4 5 abcd
aaaaa
In the first test, it is optimal to make one duplication: "dbcadabc" $$$\to$$$ "dbcadabcdbcadabc".
In the second test it is optimal to delete the last $$$3$$$ characters, then duplicate the string $$$3$$$ times, then delete the last $$$3$$$ characters to make the string have length $$$k$$$.
"abcd" $$$\to$$$ "abc" $$$\to$$$ "ab" $$$\to$$$ "a" $$$\to$$$ "aa" $$$\to$$$ "aaaa" $$$\to$$$ "aaaaaaaa" $$$\to$$$ "aaaaaaa" $$$\to$$$ "aaaaaa" $$$\to$$$ "aaaaa".
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