carloscn
commented
1 year ago Code
static int32_t count_hill_valley(int32_t *nums, size_t nums_size)
{
int32_t ret = 0;
UTILS_CHECK_PTR(nums);
UTILS_CHECK_LEN(nums_size);
size_t i = 1;
while (i < nums_size - 1) {
int32_t m = nums[i];
int32_t li = i - 1, ri = i + 1;
while (li > 0 && nums[i] == nums[li]) {
li --;
}
while (ri < nums_size && nums[i] == nums[ri]) {
ri ++;
}
ret += ((nums[i] > nums[li]) && (nums[i] > nums[ri])) ||
((nums[i] < nums[li]) && (nums[i] < nums[ri]));
i = ri;
}
finish:
return ret;
}
Description
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