Codeforces Round 651 (Div. 2) |
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Finished |
Ashish has an array $$$a$$$ of size $$$n$$$.
A subsequence of $$$a$$$ is defined as a sequence that can be obtained from $$$a$$$ by deleting some elements (possibly none), without changing the order of the remaining elements.
Consider a subsequence $$$s$$$ of $$$a$$$. He defines the cost of $$$s$$$ as the minimum between:
Note that the index of an element is its index in $$$s$$$, rather than its index in $$$a$$$. The positions are numbered from $$$1$$$. So, the cost of $$$s$$$ is equal to $$$min(max(s_1, s_3, s_5, \ldots), max(s_2, s_4, s_6, \ldots))$$$.
For example, the cost of $$$\{7, 5, 6\}$$$ is $$$min( max(7, 6), max(5) ) = min(7, 5) = 5$$$.
Help him find the minimum cost of a subsequence of size $$$k$$$.
The first line contains two integers $$$n$$$ and $$$k$$$ ($$$2 \leq k \leq n \leq 2 \cdot 10^5$$$) — the size of the array $$$a$$$ and the size of the subsequence.
The next line contains $$$n$$$ integers $$$a_1, a_2, \ldots, a_n$$$ ($$$1 \leq a_i \leq 10^9$$$) — the elements of the array $$$a$$$.
Output a single integer — the minimum cost of a subsequence of size $$$k$$$.
4 2 1 2 3 4
1
4 3 1 2 3 4
2
5 3 5 3 4 2 6
2
6 4 5 3 50 2 4 5
3
In the first test, consider the subsequence $$$s$$$ = $$$\{1, 3\}$$$. Here the cost is equal to $$$min(max(1), max(3)) = 1$$$.
In the second test, consider the subsequence $$$s$$$ = $$$\{1, 2, 4\}$$$. Here the cost is equal to $$$min(max(1, 4), max(2)) = 2$$$.
In the fourth test, consider the subsequence $$$s$$$ = $$$\{3, 50, 2, 4\}$$$. Here the cost is equal to $$$min(max(3, 2), max(50, 4)) = 3$$$.
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