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);
    }
}