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# 10.37 (Tkinter: binary search animation) Write a program that animates the binary
# search algorithm. Create a list with the numbers from 1 to 20 in this order. The
# elements are displayed in a histogram, as shown in Figure 10.18. You need to
# enter a search key in the text field. Clicking the Step button causes the program
# to perform one comparison in the algorithm. Use a light-gray color to paint the
# bars for the numbers in the current search range and use a red color to paint the
# bar indicating the middle number in the search range. When the algorithm is
# finished, display a dialog box to inform the user. Clicking the Reset button
# enables a new search to start. This button also makes the text field editable.
import tkinter.messagebox
from tkinter import *
class MainGUI:
def __init__(self):
self.lst = [x for x in range(1, 21)]
width = 380
height = 150
window = Tk()
self.cnvs = Canvas(window, width=width, height=height)
self.cnvs.pack()
frame = Frame(window)
frame.pack()
Label(frame, text="Enter a key (in float):").pack(side=LEFT)
self.key = StringVar()
Entry(frame, textvariable=self.key, justify=RIGHT, width=3).pack(side=LEFT)
Button(frame, text="Step", command=self.step).pack(side=LEFT)
Button(frame, text="Reset", command=self.reset).pack(side=LEFT)
self.reset()
window.mainloop()
def reset(self):
self.found = False
self.click = 1 # for counting number of click an odd click colors a bar with red and an even number of
# clicks colors the bars to white
self.r = len(self.lst) - 1
self.l = 0
x = 5
y = 140
self.recs = []
for i in range(20):
rect = self.cnvs.create_rectangle(x, 140, x + 18, y - 7, fill='lightgray')
self.recs.append(rect)
self.cnvs.create_text(x + 10, y-18, text=str(i + 1))
x += 18
y -= 6
def step(self):
k = int(self.key.get())
if not self.found:
mid = (self.l + self.r) // 2
self.cnvs.itemconfig(self.recs[mid], fill='red') # mark current with red
if self.click % 2 == 0:
if mid + 1 == k:
tkinter.messagebox.showinfo("showinfo", "Key is found")
self.found = True
else:
if k > self.lst[mid]:
self.l = mid + 1
for i in range(self.l):
self.cnvs.itemconfig(self.recs[i], fill='white') # change to white
else:
self.r = mid - 1
for i in range(self.r + 1, len(self.lst)):
self.cnvs.itemconfig(self.recs[i], fill='white')
if not self.found and self.l > self.r:
tkinter.messagebox.showinfo("showinfo", "Key is not found") # change to white
self.click += 1
MainGUI()
