// 2210. Count Hills and Valleys in an Array #include "leetcode.h" /* * you are given a 0-indexed integer array 'nums'. an index 'i' is part of a * hill in 'nums' if the closest non-equal neighbours of 'i' are smaller than * 'nums[i]'. similarly, an index 'i' is part of a valley in 'nums' if the * closest non-equal neighbours 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 neighbour on both the left and right of the index. return the * number of hills and valleys in 'nums'. */ int countHillValley(int *nums, int numsSize) { int prev = 0, ans = 0; for (int i = 1; i < numsSize - 1; ++i) { if (nums[prev] == nums[i] || nums[i + 1] == nums[i]) continue; if ((nums[prev] - nums[i] & INT_MIN) == (nums[i + 1] - nums[i] & INT_MIN)) ans++; prev = i; } return ans; } int main() { int n1[] = {2, 4, 1, 1, 6, 5}, n2[] = {6, 6, 5, 5, 4, 1}; printf("%d\n", countHillValley(n1, ARRAY_SIZE(n1))); // expect: 3 printf("%d\n", countHillValley(n2, ARRAY_SIZE(n2))); // expect: 0 }