Unsorted, maximum ==> sorted

https://github.com/Premiumlab/Python-for-Algorithms--Data-Structures--and-Interviews/blob/master/Mock%20Interviews/Social%20Network%20Company/Social%20Network%20Company%20-%20Interview%20Questions%20-%20SOLUTIONS/On-Site%20Question%203%20-%20SOLUTION.ipynb

On-Site Question 3 - SOLUTION

Problem

Create a function that takes in a list of unsorted prices (integers) and a maximum possible price value, and return a sorted list of prices

Requirements

Your function should be able to perform this in less than O(nlogn) time.

 

Solution

We can actually solve this problem by using a counting sort. Basically a counting sort works well when you know the range of integer values you will have ahead of time.

Read the wikipedia article linked above for a full break down, and an implementation is here below (using the prices situation described in the problem above).

def solution(unsorted_prices,max_price):

    # list of 0s at indices 0 to max_price
    prices_to_counts = [0]* (max_price+1)

    # populate prices
    for price in unsorted_prices:
        prices_to_counts[price] +=1

    # populate final sorted prices
    sorted_prices = []

    # For each price in prices_to_counts
    for price,count in enumerate(prices_to_counts):

        # for the number of times the element occurs
        for time in range(count):

            # add it to the sorted price list
            sorted_prices.append(price)

    return sorted_prices

In [3]:

solution([4,6,2,7,3,8,9],9)

Out[3]:

[2, 3, 4, 6, 7, 8, 9]

 

This was a great exercise in learning about a new sorting algorithm, make sure to read up on it and practice this problem again!

Good Job!