class Solution {
    /**
    1. 因为相邻相等的点不计数, 所以先把他们去重, 方便处理
    2. 处理后第一个数和最后一个数必定不是目标, 中间任何符合要求的数必定是目标, 统计他们即可
    */

    public int countHillValley(int[] nums) {
        List<Integer> list = new ArrayList<>();
        for (int k = 0 ; k < nums.length; k++) {
            if (list.isEmpty() || nums[k] != list.get(list.size() - 1)) list.add(nums[k]);
        }

        int count = 0;
        for (int i = 1; i <= list.size() - 2; i++){
            if (check(i, list)) {
                count++;
            }
        }

        return count;
    }

    public boolean check(int i, List<Integer> list) {
        return (list.get(i-1) < list.get(i) && list.get(i) > list.get(i+1)) 
            || (list.get(i-1) > list.get(i) && list.get(i) < list.get(i+1));
    }
}