Is Difference Between Peaks and Valleys easy or hard?

This problem is easy. It requires one linear scan and careful handling of the boundary indices. Most difficulty comes from off-by-one errors at the first and last positions, not from the algorithm itself.

How to solve Difference Between Peaks and Valleys in O(n)?

Loop from index 1 to index n-2, since the first and last elements have only one neighbor. For each index, compare nums[i] with nums[i-1] and nums[i+1]. If it is greater than both, add it to the peak sum. If it is smaller than both, add it to the valley sum, then return the difference.

Difference Between Peaks and Valleys Python or Java solution?

In Python, loop with range(1, len(nums) - 1) and use two integer variables to accumulate peaks and valleys, then return the difference. In Java, use a for loop from i = 1 to i < nums.length - 1 with two long or int accumulators. Both versions run in O(n) time and O(1) space.

What is the best approach for Difference Between Peaks and Valleys?

The best approach is a single pass over the array that updates a peak sum and a valley sum at the same time. Check each interior element against its two neighbors and add it to the correct running total. This runs in O(n) time with O(1) extra space.

What data structure is used in Difference Between Peaks and Valleys?

The problem needs only an array, which is given as input, and two integer variables for the running sums. You do not need a hash map, stack, or heap. Using lists to collect peaks and valleys is an option, but it adds O(n) space that the single-pass solution avoids.

What is the time complexity of Difference Between Peaks and Valleys?

The optimal solution runs in O(n) time because every interior element is visited once and each check uses a constant number of comparisons. The space complexity is O(1) when you use running sums instead of storing peaks and valleys in lists.

Is Difference Between Peaks and Valleys asked at Google, Amazon, or Meta?

This problem is tagged General on FleetCode and does not have a confirmed company tag in the source data. It is a short array-scan problem, so expect it as a warm-up or screening question rather than a hard round. Check company-specific question lists for the latest reports.

Description

4088. Difference Between Peaks and Valleys

Q: What is the best approach for Difference Between Peaks and Valleys?

The best approach is a single pass over the array that updates a peak sum and a valley sum at the same time. Check each interior element against its two neighbors and add it to the correct running total. This runs in O(n) time with O(1) extra space.

Q: What data structure is used in Difference Between Peaks and Valleys?

The problem needs only an array, which is given as input, and two integer variables for the running sums. You do not need a hash map, stack, or heap. Using lists to collect peaks and valleys is an option, but it adds O(n) space that the single-pass solution avoids.

Q: What is the time complexity of Difference Between Peaks and Valleys?

The optimal solution runs in O(n) time because every interior element is visited once and each check uses a constant number of comparisons. The space complexity is O(1) when you use running sums instead of storing peaks and valleys in lists.

Q: Is Difference Between Peaks and Valleys asked at Google, Amazon, or Meta?

This problem is tagged General on FleetCode and does not have a confirmed company tag in the source data. It is a short array-scan problem, so expect it as a warm-up or screening question rather than a hard round. Check company-specific question lists for the latest reports.

Easy81.7% acceptance

You are given an integer array nums of length n.

An index i is called a peak if all of the following conditions hold:

0 < i < n - 1
nums[i] > nums[i - 1]
nums[i] > nums[i + 1]

An index i is called a valley if all of the following conditions hold:

0 < i < n - 1
nums[i] < nums[i - 1]
nums[i] < nums[i + 1]

Return an integer denoting the difference between the sum of all peak values and the sum of all valley values.

Example 1:

Input: nums = [1,5,2,4,1,3,0]

Output: 9

Explanation:

The peak values are nums[1] = 5, nums[3] = 4, and nums[5] = 3.
The valley values are nums[2] = 2 and nums[4] = 1.
The difference between the sum of the peak values and the sum of the valley values is (5 + 4 + 3) - (2 + 1) = 9. Hence, the answer is 9.

Example 2:

Input: nums = [-5,-6,-1,-2,5,3,2]

Output: 12

Explanation:

The peak values are nums[2] = -1 and nums[4] = 5.
The valley values are nums[1] = -6 and nums[3] = -2.
The difference between the sum of the peak values and the sum of the valley values is (-1 + 5) - (-6 + (-2)) = 12. Hence, the answer is 12.

Example 3:

Input: nums = [6,5,2,5,5,3,6]

Output: -5

Explanation:

There are no peak values in the array.
The valley values are nums[2] = 2 and nums[5] = 3.
The difference between the sum of the peak values and the sum of the valley values is (0) - (2 + 3) = -5. Hence, the answer is -5.

Constraints:

3 <= n == nums.length <= 100
-100 <= nums[i] <= 100

LanguageLoading editor…

1class Solution:
2    def peakValleyDifference(self, nums: list[int]) -> int:
3        

Starter codePython 3Spaces: 4

Examples

Case 1Case 2Case 3

Input

[1,5,2,4,1,3,0]

Input

[-5,-6,-1,-2,5,3,2]

Input

[6,5,2,5,5,3,6]

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