Python Bubble sort

Question

Hey so the code works perfectly thank you very much!

i just have one more question. I want to have an arrow displayed in between the two coulmns. i created this code but i dont really know how to make it go in between the columns that are being switched. any suggestions?

def arrow(lst, i):                 # function for the arrow
if (lst[i], lst[i+1] == lst[i+1], lst[i]):
    t.home()
    t.penup()
                     # im thinking something goes here but i dont know what :P
    t.pendown()
    t.pencolor("red")
    t.right(90)
    t.forward(20)

any help would be very appreciated! Thank you! btw the rest of the code is like imran's code! :) thank yoU!

Answer 1

your code looks a lot like one of the versions of bubble sort here. The main issue why your version isn't working is because you are comparing lst at index i with i-1 which fails when i=0. Change that section to:

        if (lst[i] < lst[i + 1]):
            swapped = False
            lst[i+1], lst[i] = lst[i], lst[i+1]

Also, don't define n outside of the function (which should ideally be called bubble_sort, or something similar), that is bad programming, a bug waiting to happen. I don't know what you are trying to accomplish with lst = [lst]. Might want to use a different variable name.

Edit: I made some liberal changes to your code. I put all the drawing call inside the bubble sort. The bubble sort also internally converts the list into a list of tuples where the second element of the tuple is the color. The for loop at the end of your code doesn't do anything worthwhile. I think your main issue was that it was not pausing between each iteration of the while loop so you don't get to see the elements of the list bubble up.

#!/usr/bin/python
import turtle as t

def draw(lst, width):
  for x in lst:
    height = x[0]
    t.color(x[1])
    t.forward(width)
    t.left(90)
    t.forward(height)
    t.left(90)
    t.forward(width)
    t.left(90)
    t.forward(height)
    t.left(90)
    t.penup()
    t.forward(30)
    t.pendown()

def bubble_sort(orig_lst):  
  lst = [ (x, "blue") for x in orig_lst ]
  n = len(lst)-1 
  t.pensize(3)
  draw(lst, width)
  swapped = True  
  while swapped:  
    swapped = False  
    for i in range(n):  
        if lst[i+1][0] < lst[i][0]:  
            lst[i], lst[i+1] = lst[i+1], lst[i]
            lst[i] = (lst[i][0], "green")  
            swapped = True 
            next = raw_input("hit any key to continue ")
            t.home()
            t.clear() 
            draw(lst,width)
  newLst = [ x[0] for x in lst ]
  return newLst

# TOP LEVEL
original_lst = input("Enter list to be sorted: ")
width = input("Provide the width: ")

newLst = bubble_sort(original_lst)
print "Done! Sorted list is: ", newLst
next = raw_input("hit any key to exit ")