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

I wrote a bubble sort based on your code:

import types

def bubble_sort(lst):
    assert(type(lst)==types.ListType)
    for index in range(1,len(lst)):
        while index > 0 and lst[index-1] > lst[index]:
            lst[index-1] , lst[index] = lst[index] , lst[index-1]
            index -= 1
    return

lst = input("Enter list to be sorted: ")
print "Original: ",lst
bubble_sort(lst)
print "Sorted: ",lst

The test looks like:

C:\Users\NAME\Desktop>bubble.py
Enter list to be sorted: [4, 24, 25, 2, 6, -1, 73, 1]
Original:  [4, 24, 25, 2, 6, -1, 73, 1]
Sorted:  [-1, 1, 2, 4, 6, 24, 25, 73]

Hope it helps!

Answer 2

There are just a few things to edit from your original code, it is better to have two for loops for this to check the values for this. Also before you had [i-1] which defeats the purpose of a bubble sort as you are sorting from left to right if that makes sense. Anyways here is what I have done.

def swap(lst):
    for i in range (len(lst)):
        for j in range (len(lst)-1):
            if lst[j] > lst[j+1]:
                lst[j], lst[j+1] = lst[j+1], lst[j]
                print (lst)


lst = input("Enter list to be sorted: ")
print (lst)
swap(lst)

Answer 3

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 ")