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

 import java.util.Scanner;
 public class Main {
     public static void main(String[] args) {
         Scanner cin = new Scanner(System.in);
         int n = cin.nextInt();
         int[] arr = new int[n];
         for (int i = 0; i < n; i++)
             arr[i] = cin.nextInt();
         int ans = 0;
         for (int i = 1; i < n - 1; i++)
             if (arr[i] < arr[i - 1] && arr[i] < arr[i + 1] || arr[i] > arr[i - 1] && arr[i] > arr[i + 1])
                 ans++;
         System.out.println(ans);
     }
 }