2210. Count Hills and Valleys in an Array

You are given a 0-indexed integer array nums. An index i is part of a hill in nums if the closest non-equal neighbors of i are smaller than nums[i]. Similarly, an index i is part of a valley in nums if the closest non-equal neighbors of i are larger than nums[i]. Adjacent indices i and j are part of the same hill or valley if nums[i] == nums[j].

Note that for an index to be part of a hill or valley, it must have a non-equal neighbor on both the left and right of the index.

Return the number of hills and valleys in nums.

class Solution {
public:
    int countHillValley(vector<int>& nums) {
        int res = 0, n = nums.size();
        for(int i = 0; i < n; i++) {
            int l = i - 1, r = i + 1;
            if(i > 0 and nums[i] == nums[i-1]) continue;
            while(l >= 0 and nums[l] == nums[i]) l--;
            while(r < n and nums[r] == nums[i]) r++;
            if(l < 0 or r >= n) continue;
            if(nums[l] < nums[i] and nums[r] < nums[i]) res++;
            else if(nums[l] > nums[i] and nums[r] > nums[i]) res++;
        }
        return res;
    }
};