Sorting Algorithm Visualization : Quick Sort

Last Updated : 21 Jun, 2020

An algorithm like Quicksort algorithm is hard to understand theoretically. We can understand easily by visualizing such kind of algorithms. In this article, a program that visualizes the Quicksort Algorithm has been implemented.
The Graphical User Interface(GUI) is implemented in python using pygame library.
Approach:

An array of random values is generated and are drawn as lines(bars) in the window.
Since the algorithm performs the operation very fast, pygame.time.delay() has been used to slow down the process.
Assign specific keys for each operation (start sorting, reset bars).
The actions are performed using ‘pygame.event.get()’ method, which stores all the events which user performs.
Different colors are used to indicate types of bar.
- Green – Unsorted bar
- Blue – Pivot bar
- Orange – Sorted bar

Examples:

Attention reader! Don’t stop learning now. Get hold of all the important DSA concepts with the DSA Self Paced Course at a student-friendly price and become industry ready. To complete your preparation from learning a language to DS Algo and many more, please refer Complete Interview Preparation Course.

In case you wish to attend live classes with experts, please refer DSA Live Classes for Working Professionals and Competitive Programming Live for Students.

Input:
Press “Enter” key to Perform Visualization.
Press “r” key to generate new array.
Output:
Initial:

Sorting:

Final:

Please make sure to install the pygame library in your system.

Below is the implementation of the above visualizer:

Python

# Python implementation of the 
# Sorting visualiser: Quick Sort
  
# Imports
import pygame
import random
pygame.font.init()
  
# Total window
screen = pygame.display.set_mode(
            (900, 650)
        )
  
# Title and Icon 
pygame.display.set_caption("SORTING VISUALISER")
  
# Uncomment below lines for setting 
# up the icon for the visuliser
# img = pygame.image.load('sort_icon.png')
# pygame.display.set_icon(img)
  
# Boolean variable to run 
# the program in while loop
run = True
  
# Window size and some initials
width = 900
length = 600
array =[0]*151
arr_clr =[(0, 204, 102)]*151
clr_ind = 0
clr =[(0, 204, 102), (255, 0, 0),\
      (0, 0, 153), (255, 102, 0)]
fnt = pygame.font.SysFont("comicsans", 30)
fnt1 = pygame.font.SysFont("comicsans", 20)
  
  
# Function to generate new Array
def generate_arr():
    for i in range(1, 151):
        arr_clr[i]= clr[0]
        array[i]= random.randrange(1, 100)
          
# Intially generate a array
generate_arr() 
  
# Function to refill the 
# updates on the window
def refill():
    screen.fill((255, 255, 255))
    draw()
    pygame.display.update()
    pygame.time.delay(30)
      
# Sorting Algo:Quick sort
def quicksort(array, l, r):
    if l<r:
        pi = partition(array, l, r)
        quicksort(array, l, pi-1)
        refill()
        for i in range(0, pi + 1):
            arr_clr[i]= clr[3]
        quicksort(array, pi + 1, r)
          
# Function to partition the array
def partition(array, low, high):
    pygame.event.pump() 
    pivot = array[high]
    arr_clr[high]= clr[2]
    i = low-1
    for j in range(low, high):
        arr_clr[j]= clr[1]
        refill()
        arr_clr[high]= clr[2]
        arr_clr[j]= clr[0]
        arr_clr[i]= clr[0]
        if array[j]<pivot:
            i = i + 1
            arr_clr[i]= clr[1]
            array[i], array[j]= array[j], array[i]
    refill()
    arr_clr[i]= clr[0]
    arr_clr[high]= clr[0]
    array[i + 1], array[high] = array[high], array[i + 1] 
      
    return ( i + 1 )
      
# Function to Draw the 
# array values
def draw():
    # Text should be rendered
    txt = fnt.render("SORT : PRESS 'ENTER'",\
                       1, (0, 0, 0))
      
    # Position where text is placed
    screen.blit(txt, (20, 20))
    txt1 = fnt.render("NEW ARRAY : PRESS 'R'",\
                      1, (0, 0, 0))
    screen.blit(txt1, (20, 40))
    txt2 = fnt1.render("ALGORITHM USED: QUICK SORT",\
                       1, (0, 0, 0))
    screen.blit(txt2, (600, 60))
    element_width =(width-150)//150
    boundry_arr = 900 / 150
    boundry_grp = 550 / 100
    pygame.draw.line(screen, (0, 0, 0),\
                (0, 95), (900, 95), 6)
      
    # Drawing the array values as lines
    for i in range(1, 151):
        pygame.draw.line(screen,\
                arr_clr[i], (boundry_arr * i-3, 100),\
                (boundry_arr * i-3,\
                 array[i]*boundry_grp + 100),\
                 element_width)
                   
# Program should be run
# continuously to keep the window open
while run:
    # background
    screen.fill((255, 255, 255))
      
    # Event handler stores all event 
    for event in pygame.event.get():
          
        # If we click Close button in window
        if event.type == pygame.QUIT:
            run = False
        if event.type == pygame.KEYDOWN:
            if event.key == pygame.K_r:
                generate_arr() 
            if event.key == pygame.K_RETURN:
                quicksort(array, 1, len(array)-1)     
    draw()
    pygame.display.update()
      
pygame.quit()

Output:

My Personal Notes

Related Articles

Related Articles

Sorting Algorithm Visualization : Quick Sort

Python