{ "data": { "question": { "questionId": "2316", "questionFrontendId": "2210", "categoryTitle": "Algorithms", "boundTopicId": 1341995, "title": "Count Hills and Valleys in an Array", "titleSlug": "count-hills-and-valleys-in-an-array", "content": "

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].

\n\n

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.

\n\n

Return the number of hills and valleys in nums.

\n\n

 

\n

Example 1:

\n\n
\nInput: nums = [2,4,1,1,6,5]\nOutput: 3\nExplanation:\nAt index 0: There is no non-equal neighbor of 2 on the left, so index 0 is neither a hill nor a valley.\nAt index 1: The closest non-equal neighbors of 4 are 2 and 1. Since 4 > 2 and 4 > 1, index 1 is a hill. \nAt index 2: The closest non-equal neighbors of 1 are 4 and 6. Since 1 < 4 and 1 < 6, index 2 is a valley.\nAt 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.\nAt index 4: The closest non-equal neighbors of 6 are 1 and 5. Since 6 > 1 and 6 > 5, index 4 is a hill.\nAt index 5: There is no non-equal neighbor of 5 on the right, so index 5 is neither a hill nor a valley. \nThere are 3 hills and valleys so we return 3.\n
\n\n

Example 2:

\n\n
\nInput: nums = [6,6,5,5,4,1]\nOutput: 0\nExplanation:\nAt index 0: There is no non-equal neighbor of 6 on the left, so index 0 is neither a hill nor a valley.\nAt index 1: There is no non-equal neighbor of 6 on the left, so index 1 is neither a hill nor a valley.\nAt 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.\nAt 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.\nAt 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.\nAt index 5: There is no non-equal neighbor of 1 on the right, so index 5 is neither a hill nor a valley.\nThere are 0 hills and valleys so we return 0.\n
\n\n

 

\n

Constraints:

\n\n\n", "translatedTitle": "统计数组中峰和谷的数量", "translatedContent": "

给你一个下标从 0 开始的整数数组 nums 。如果两侧距 i 最近的不相等邻居的值均小于 nums[i] ,则下标 inums 中,某个峰的一部分。类似地,如果两侧距 i 最近的不相等邻居的值均大于 nums[i] ,则下标 inums 中某个谷的一部分。对于相邻下标 ij ,如果 nums[i] == nums[j] , 则认为这两下标属于 同一个 峰或谷。

\n\n

注意,要使某个下标所做峰或谷的一部分,那么它左右两侧必须 存在不相等邻居。

\n\n

返回 nums 中峰和谷的数量。

\n\n

 

\n\n

示例 1:

\n\n
\n输入:nums = [2,4,1,1,6,5]\n输出:3\n解释:\n在下标 0 :由于 2 的左侧不存在不相等邻居,所以下标 0 既不是峰也不是谷。\n在下标 1 :4 的最近不相等邻居是 2 和 1 。由于 4 > 2 且 4 > 1 ,下标 1 是一个峰。\n在下标 2 :1 的最近不相等邻居是 4 和 6 。由于 1 < 4 且 1 < 6 ,下标 2 是一个谷。\n在下标 3 :1 的最近不相等邻居是 4 和 6 。由于 1 < 4 且 1 < 6 ,下标 3 符合谷的定义,但需要注意它和下标 2 是同一个谷的一部分。\n在下标 4 :6 的最近不相等邻居是 1 和 5 。由于 6 > 1 且 6 > 5 ,下标 4 是一个峰。\n在下标 5 :由于 5 的右侧不存在不相等邻居,所以下标 5 既不是峰也不是谷。\n共有 3 个峰和谷,所以返回 3 。
\n\n

示例 2:

\n\n
\n输入:nums = [6,6,5,5,4,1]\n输出:0\n解释:\n在下标 0 :由于 6 的左侧不存在不相等邻居,所以下标 0 既不是峰也不是谷。\n在下标 1 :由于 6 的左侧不存在不相等邻居,所以下标 1 既不是峰也不是谷。\n在下标 2 :5 的最近不相等邻居是 6 和 4 。由于 5 < 6 且 5 > 4 ,下标 2 既不是峰也不是谷。\n在下标 3 :5 的最近不相等邻居是 6 和 4 。由于 5 < 6 且 5 > 4 ,下标 3 既不是峰也不是谷。\n在下标 4 :4 的最近不相等邻居是 5 和 1 。由于 4 < 5 且 4 > 1 ,下标 4 既不是峰也不是谷。\n在下标 5 :由于 1 的右侧不存在不相等邻居,所以下标 5 既不是峰也不是谷。\n共有 0 个峰和谷,所以返回 0 。\n
\n\n

 

\n\n

提示:

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