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# 10.38 (Tkinter: selection-sort animation) Write a program that animates the selection-sort
# algorithm. Create a list that consists of 20 distinct numbers from 1 to 20 in a random
# order. The elements are displayed in a histogram, as shown in Figure 10.19.
# Clicking the Step button causes the program to perform an iteration of the outer
# loop in the algorithm and repaints the histogram for the new list. Color the last bar
# in the sorted sublist. When the algorithm is finished, display a dialog box to inform
# the user. Clicking the Reset button creates a new random list for a new start.
from tkinter import * # Import tkinter
import tkinter.messagebox
import random
class StepControl:
def __init__(self):
self.list = [x for x in range(1, 20)]
self.reset()
self.key = 0
def reset(self):
self.i = 0 # current index
self.done = False
random.shuffle(self.list)
self.drawAStep()
def step(self):
if self.i > len(self.list) - 1:
tkinter.messagebox.showinfo("showinfo", "The list is already sorted")
return
# Find the minimum in the list[i..list.length-1]
currentMin = self.list[self.i]
currentMinIndex = self.i
for j in range(self.i + 1, len(self.list)):
if currentMin > self.list[j]:
currentMin = self.list[j];
currentMinIndex = j;
# Swap list[i] with list[currentMinIndex] if necessary;
if currentMinIndex != self.i:
self.list[currentMinIndex] = self.list[self.i]
self.list[self.i] = currentMin
self.drawAStep()
self.i += 1 # Increase step
def drawAStep(self):
bottomGap = 10
canvas.delete("line")
canvas.create_line(10, height - bottomGap, width - 10, height - bottomGap, tag="line")
barWidth = (width - 20) / len(self.list)
maxCount = int(max(self.list))
for i in range(len(self.list)):
canvas.create_rectangle(i * barWidth + 10, (height - bottomGap) * (1 - self.list[i] / (maxCount + 4)),
(i + 1) * barWidth + 10, height - bottomGap, tag="line")
canvas.create_text(i * barWidth + 10 + barWidth / 2,
(height - bottomGap) * (1 - self.list[i] / (maxCount + 4)) - 8,
text=str(self.list[i]), tag="line")
if self.i >= 0:
canvas.create_rectangle(self.i * barWidth + 10,
(height - bottomGap) * (1 - self.list[self.i] / (maxCount + 4)),
(self.i + 1) * barWidth + 10, height - bottomGap, fill="red", tag="line")
def step():
control.step()
def reset():
control.reset()
window = Tk() # Create a window
window.title("Selection Sort Animation") # Set title
width = 340
height = 150
radius = 2
canvas = Canvas(window, width=width, height=height)
canvas.pack()
frame = Frame(window)
frame.pack()
Button(frame, text="Step", command=step).pack(side=LEFT)
Button(frame, text="Reset", command=reset).pack(side=LEFT)
control = StepControl()
control.drawAStep()
window.mainloop() # Create an event loop
