CODEWITHSUNDEEP
python
Zeus
Zeus

Reputation: 2253

Finding peak in an array

I'm completely new to Python, thus the question. I'm trying to solve a standard interview question, which is finding a peak in an array A peak is defined as a number which is greater than it's left and right neighbor. I'm trying to find the largest such peak.

This is my code

#!/usr/bin/python3

def main():
    arr = [7, 12, 13, 8, 2, 16, 24, 11, 5, 1]
    num = find_peak(arr)
    print(num)

def find_peak(arr):
    return find_peak(arr, 0, len(arr))

def find_peak(arr, start, stop):

    mid = (start + stop)/2

    if(arr[mid] > arr[mid-1] and arr[mid] > arr[mid+1]):
        return arr[mid]
    elif (arr[mid] < arr[mid -1]):
        find_peak(arr, 0, mid-1)
    elif (arr[mid] < arr[mid+1]):
        find_peak(arr, mid+1, stop)

if __name__ == '__main__':
    main()

This is the error that I'm getting 

Traceback (most recent call last):
  File "peak.py", line 23, in <module>
    main()
  File "peak.py", line 5, in main
    num = find_peak(arr)
TypeError: find_peak() missing 2 required positional arguments: 'start' and 'stop'

Any help appreciated

Upvotes: 0

Views: 365

Answers (4)

vinycd
vinycd

Reputation: 97

Overloading is not allowed in Python, my suggestion is to use default values instead of two functions

def find_peak(arr, start = 0, stop = 0):
    if stop == 0:
        stop = len(arr)

    mid = (start + stop)/2

    if(arr[mid] > arr[mid-1] and arr[mid] > arr[mid+1]):
        return arr[mid]
    elif (arr[mid] < arr[mid -1]):
        find_peak(arr, 0, mid-1)
    elif (arr[mid] < arr[mid+1]):
        find_peak(arr, mid+1, stop)

Upvotes: 0

Mostafa Wattad
Mostafa Wattad

Reputation: 61

def main():
    arr = [7, 12, 13, 8, 2, 16, 24, 11, 5, 1]
    num = find_peak(arr)
    print(num)

def find_peak(arr):
    return find_peaks(arr, 0, len(arr))

def find_peaks(arr, start, stop):

    mid = (start + stop)/2

    if(arr[mid] > arr[mid-1] and arr[mid] > arr[mid+1]):
        return arr[mid]
    elif (arr[mid] < arr[mid -1]):
        find_peaks(arr, 0, mid-1)
    elif (arr[mid] < arr[mid+1]):
        find_peaks(arr, mid+1, stop)

    if __name__ == '__main__':
       main()

Upvotes: 0

user2209008
user2209008

Reputation:

You are calling this:

num = find_peak(arr)

But find_peak takes 3 arguments, as the error states. You have only supplied one.

Unlike C++ or other languages, you cannot have a function with the same name that takes different arguments (also known as function overloading). You can, however, define optional arguments in the function declaration.

Upvotes: 0

mhlester
mhlester

Reputation: 23251

You've got two function definitions for find_peak, one with one argument arr and the other with three arguments arr, start, and stop. The second one overwrites the first one.

Use two different names for two different functions

Upvotes: 4

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