Find the Peaks

Problem Description

You are given a 0-indexed array mountain. Your task is to find all the peaks in the mountain array. A peak is defined as an element that is strictly greater than its neighboring elements. The first and last elements of the array are not a peak. Return an array that consists of indices of peaks in the given array in any order.

Key Insights

• A peak is an element that is greater than its adjacent elements.
• The first and last elements cannot be peaks.
• We need to iterate through the array and check each element (except the first and last) to see if it satisfies the peak condition.

Space and Time Complexity

Time Complexity: O(n), where n is the length of the array. We need to check each element once. Space Complexity: O(k), where k is the number of peaks found, since we store the indices of the peaks.

Solution

To solve the problem, we will:

1. Initialize an empty list to store the indices of the peaks.
2. Loop through the array starting from index 1 to the second last index (n-2).
3. For each element, check if it is greater than its neighbors (previous and next elements).
4. If it is a peak, we append its index to the list.
5. Finally, return the list of indices.

The main data structure used is a list to collect the indices of peaks.

Code Solutions