Mountain Peak

Unit 2 Session A

U-nderstand

Understand what the interviewer is asking for by using test cases and questions about the problem.

• Can there be multiple peaks in the mountain array?
  • No. By our definition of mountain array, there will only ever be one peak.
• What if the array is empty?
  • The array will always have at least 3 elements.

P-lan

Plan the solution with appropriate visualizations and pseudocode.

General Idea: Loop through each middle element and compare it to the element after. If it's larger than the next element, we've found the peak.

1) Loop through the middle elements of the array (skip the beginning/end)
2) Compare each element to the next element 
  a) If the next element is bigger, keep looking
  b) If the next element is smaller, return the current element

I-mplement

def peak_index_in_mountain_array(arr):
    for i in range(1, len(arr) - 1):
        if arr[i] > arr[i + 1]:
            return i