Code of mergesort implemented in Python, ploted using matplotlib.

mergesort.py

from random import randint
from timeit import timeit
import matplotlib.pyplot as plt

def reverseArray(lenght):
	a = []
	for i in range(lenght):
		a.append(lenght-i)
	return a

def randomArray(length):
	array = []
	tmp = 0
	while tmp < length:
		num = randint(1, length*10)
		if num not in array:
			array.append(num)
			tmp += 1
	return array

def mergeSort(array):
	if len(array) > 1:
		half = len(array) // 2
		lArray = array[:half]
		rArray = array[half:]

		mergeSort(lArray)
		mergeSort(rArray)

		lMark, rMark, position = 0, 0, 0

		while lMark < len(lArray) and rMark < len(rArray):
			if lArray[lMark] < rArray[rMark]:
				array[position] = lArray[lMark]
				lMark += 1
			else:
				array[position] = rArray[rMark]
				rMark += 1
			position += 1

		while lMark < len(lArray):
			array[position] = lArray[lMark]
			lMark += 1
			position += 1
		while rMark < len(rArray):
			array[position] = rArray[rMark]
			rMark += 1
			position += 1
			
timeRandom = []
timeReverse = []
lengths = []
elements = [1000, 3000, 6000, 9000, 12000, 15000, 18000, 21000, 24000]

def desenhaGrafico(xl = "Qnt. Elements(und)", yl = "Time(sec)"):
  
	fig = plt.figure(figsize=(10, 8))
	plt.title('Mergesort Analysis', fontsize=20)
	plt.plot(lengths, timeRandom, label = "Mergesort - Random")
	plt.plot(lengths, timeReverse, label = "Mergesort - Reverse")
	legend = plt.legend(loc='upper left', shadow=True)
	frame = legend.get_frame()
	frame.set_facecolor('0.90')
	
	plt.xlabel(xl)
	plt.ylabel(yl)
	
	fig.savefig('graph.png')
	
def main():
	for _tmp in elements:
		lengths.append(_tmp)
		arrayRandom = randomArray(_tmp)
		arrayReverse = reverseArray(_tmp)
		timeRandom.append(timeit("mergeSort({})".format(arrayRandom), 
			setup = "from __main__ import mergeSort", number = 1))
		timeReverse.append(timeit("mergeSort({})".format(arrayReverse), 
			setup = "from __main__ import mergeSort", number = 1))
		
	desenhaGrafico()

if __name__ == "__main__":
	main()