CCF2016.4 - A题

思路：枚举每个点，看看它是否同时小于/大于前一个点和后一个点

 1 import java.util.Scanner;
 2 public class Main {
 3     public static void main(String[] args) {
 4         Scanner cin = new Scanner(System.in);
 5         int n = cin.nextInt();
 6         int[] arr = new int[n];
 7         for (int i = 0; i < n; i++)
 8             arr[i] = cin.nextInt();
 9         int ans = 0;
10         for (int i = 1; i < n - 1; i++)
11             if (arr[i] < arr[i - 1] && arr[i] < arr[i + 1] || arr[i] > arr[i - 1] && arr[i] > arr[i + 1])
12                 ans++;
13         System.out.println(ans);
14     }
15 }