CF1495B.Let's Go Hiking
普及/提高-
通过率:0%
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题目描述
On a weekend, Qingshan suggests that she and her friend Daniel go hiking. Unfortunately, they are busy high school students, so they can only go hiking on scratch paper.
A permutation p is written from left to right on the paper. First Qingshan chooses an integer index x ( 1≤x≤n ) and tells it to Daniel. After that, Daniel chooses another integer index y ( 1≤y≤n , y=x ).
The game progresses turn by turn and as usual, Qingshan moves first. The rules follow:
- If it is Qingshan's turn, Qingshan must change x to such an index x′ that 1≤x′≤n , ∣x′−x∣=1 , x′=y , and px′<px at the same time.
- If it is Daniel's turn, Daniel must change y to such an index y′ that 1≤y′≤n , ∣y′−y∣=1 , y′=x , and py′>py at the same time.
The person who can't make her or his move loses, and the other wins. You, as Qingshan's fan, are asked to calculate the number of possible x to make Qingshan win in the case both players play optimally.
输入格式
The first line contains a single integer n ( 2≤n≤105 ) — the length of the permutation.
The second line contains n distinct integers p1,p2,…,pn ( 1≤pi≤n ) — the permutation.
输出格式
Print the number of possible values of x that Qingshan can choose to make her win.
输入输出样例
输入#1
5 1 2 5 4 3
输出#1
1
输入#2
7 1 2 4 6 5 3 7
输出#2
0
说明/提示
In the first test case, Qingshan can only choose x=3 to win, so the answer is 1 .
In the second test case, if Qingshan will choose x=4 , Daniel can choose y=1 . In the first turn (Qingshan's) Qingshan chooses x′=3 and changes x to 3 . In the second turn (Daniel's) Daniel chooses y′=2 and changes y to 2 . Qingshan can't choose x′=2 because y=2 at this time. Then Qingshan loses.