A11189 | Maximum of Maximums of Minimums
时间限制1s
内存限制256MB
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题目描述
You are given an array $a_{1},a_{2},...,a_{n}$ consisting of $n$ integers, and an integer $k$ . You have to split the array into exactly $k$ non-empty subsegments. You'll then compute the minimum integer on each subsegment, and take the maximum integer over the $k$ obtained minimums. What is the maximum possible integer you can get?
Definitions of subsegment and array splitting are given in notes.
Definitions of subsegment and array splitting are given in notes.
输入格式
The first line contains two integers $n$ and $k$ ( $1<=k<=n<=10^{5}$ ) — the size of the array $a$ and the number of subsegments you have to split the array to.
The second line contains $n$ integers $a_{1},a_{2},...,a_{n}$ ( $-10^{9}<=a_{i}<=10^{9}$ ).
The second line contains $n$ integers $a_{1},a_{2},...,a_{n}$ ( $-10^{9}<=a_{i}<=10^{9}$ ).
输出格式
Print single integer — the maximum possible integer you can get if you split the array into $k$ non-empty subsegments and take maximum of minimums on the subsegments.
输入输出样例
输入 #1
5 2 1 2 3 4 5
输出 #1
5
输入 #2
5 1 -4 -5 -3 -2 -1
输出 #2
-5
A subsegment $[l,r]$ ( $l<=r$ ) of array $a$ is the sequence $a_{l},a_{l+1},...,a_{r}$ .
Splitting of array $a$ of $n$ elements into $k$ subsegments $[l_{1},r_{1}]$ , $[l_{2},r_{2}]$ , ..., $[l_{k},r_{k}]$ ( $l_{1}=1$ , $r_{k}=n$ , $l_{i}=r_{i-1}+1$ for all $i>1$ ) is $k$ sequences $(a_{l1},...,a_{r1}),...,(a_{lk},...,a_{rk})$ .
In the first example you should split the array into subsegments $[1,4]$ and $[5,5]$ that results in sequences $(1,2,3,4)$ and $(5)$ . The minimums are $min(1,2,3,4)=1$ and $min(5)=5$ . The resulting maximum is $max(1,5)=5$ . It is obvious that you can't reach greater result.
In the second example the only option you have is to split the array into one subsegment $[1,5]$ , that results in one sequence $(-4,-5,-3,-2,-1)$ . The only minimum is $min(-4,-5,-3,-2,-1)=-5$ . The resulting maximum is $-5$ .
Splitting of array $a$ of $n$ elements into $k$ subsegments $[l_{1},r_{1}]$ , $[l_{2},r_{2}]$ , ..., $[l_{k},r_{k}]$ ( $l_{1}=1$ , $r_{k}=n$ , $l_{i}=r_{i-1}+1$ for all $i>1$ ) is $k$ sequences $(a_{l1},...,a_{r1}),...,(a_{lk},...,a_{rk})$ .
In the first example you should split the array into subsegments $[1,4]$ and $[5,5]$ that results in sequences $(1,2,3,4)$ and $(5)$ . The minimums are $min(1,2,3,4)=1$ and $min(5)=5$ . The resulting maximum is $max(1,5)=5$ . It is obvious that you can't reach greater result.
In the second example the only option you have is to split the array into one subsegment $[1,5]$ , that results in one sequence $(-4,-5,-3,-2,-1)$ . The only minimum is $min(-4,-5,-3,-2,-1)=-5$ . The resulting maximum is $-5$ .
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评测结果：Accepted