Package g2201_2300.s2210_count_hills_and_valleys_in_an_array

Class Solution

  • public class Solution
extends Object
    2210 - Count Hills and Valleys in an Array.

    Easy

    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.

    Example 1:

    Input: nums = [2,4,1,1,6,5]

    Output: 3

    Explanation:

    At index 0: There is no non-equal neighbor of 2 on the left, so index 0 is neither a hill nor a valley.

    At index 1: The closest non-equal neighbors of 4 are 2 and 1. Since 4 > 2 and 4 > 1, index 1 is a hill.

    At index 2: The closest non-equal neighbors of 1 are 4 and 6. Since 1 < 4 and 1 < 6, index 2 is a valley.

    At index 3: The closest non-equal neighbors of 1 are 4 and 6. Since 1 < 4 and 1 < 6, index 3 is a valley, but note that it is part of the same valley as index 2. At index 4: The closest non-equal neighbors of 6 are 1 and 5. Since 6 > 1 and 6 > 5, index 4 is a hill.

    At index 5: There is no non-equal neighbor of 5 on the right, so index 5 is neither a hill nor a valley. There are 3 hills and valleys so we return 3.

    Example 2:

    Input: nums = [6,6,5,5,4,1]

    Output: 0

    Explanation:

    At index 0: There is no non-equal neighbor of 6 on the left, so index 0 is neither a hill nor a valley.

    At index 1: There is no non-equal neighbor of 6 on the left, so index 1 is neither a hill nor a valley.

    At index 2: The closest non-equal neighbors of 5 are 6 and 4. Since 5 < 6 and 5 > 4, index 2 is neither a hill nor a valley.

    At index 3: The closest non-equal neighbors of 5 are 6 and 4. Since 5 < 6 and 5 > 4, index 3 is neither a hill nor a valley.

    At index 4: The closest non-equal neighbors of 4 are 5 and 1. Since 4 < 5 and 4 > 1, index 4 is neither a hill nor a valley.

    At index 5: There is no non-equal neighbor of 1 on the right, so index 5 is neither a hill nor a valley. There are 0 hills and valleys so we return 0.

    Constraints:

    • 3 <= nums.length <= 100
    • 1 <= nums[i] <= 100

    • Constructor Detail

      • Solution

        public Solution()

    • Method Detail

      • countHillValley

        public int countHillValley​(int[] nums)