Package g2201_2300.s2210_count_hills_and_valleys_in_an_array

Class Solution

java.lang.Object
g2201_2300.s2210_count_hills_and_valleys_in_an_array.Solution
public class Solution extends Object
2210 - Count Hills and Valleys in an Array.<p>Easy</p> <p>You are given a <strong>0-indexed</strong> integer array <code>nums</code>. An index <code>i</code> is part of a <strong>hill</strong> in <code>nums</code> if the closest non-equal neighbors of <code>i</code> are smaller than <code>nums[i]</code>. Similarly, an index <code>i</code> is part of a <strong>valley</strong> in <code>nums</code> if the closest non-equal neighbors of <code>i</code> are larger than <code>nums[i]</code>. Adjacent indices <code>i</code> and <code>j</code> are part of the <strong>same</strong> hill or valley if <code>nums[i] == nums[j]</code>.</p> <p>Note that for an index to be part of a hill or valley, it must have a non-equal neighbor on <strong>both</strong> the left and right of the index.</p> <p>Return <em>the number of hills and valleys in</em> <code>nums</code>.</p> <p><strong>Example 1:</strong></p> <p><strong>Input:</strong> nums = [2,4,1,1,6,5]</p> <p><strong>Output:</strong> 3</p> <p><strong>Explanation:</strong></p> <p>At index 0: There is no non-equal neighbor of 2 on the left, so index 0 is neither a hill nor a valley.</p> <p>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.</p> <p>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.</p> <p>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.</p> <p>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.</p> <p><strong>Example 2:</strong></p> <p><strong>Input:</strong> nums = [6,6,5,5,4,1]</p> <p><strong>Output:</strong> 0</p> <p><strong>Explanation:</strong></p> <p>At index 0: There is no non-equal neighbor of 6 on the left, so index 0 is neither a hill nor a valley.</p> <p>At index 1: There is no non-equal neighbor of 6 on the left, so index 1 is neither a hill nor a valley.</p> <p>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.</p> <p>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.</p> <p>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.</p> <p>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.</p> <p><strong>Constraints:</strong></p> <ul> <li><code>3 <= nums.length <= 100</code></li> <li><code>1 <= nums[i] <= 100</code></li> </ul>

  • Constructor Details

    • Solution

      public Solution()

  • Method Details

    • countHillValley

      public int countHillValley(int[] nums)