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PyQt5 – Binary Search Visualizer

  • Last Updated : 03 May, 2020

In this article we will see how we can make a PyQt5 application which will visualize the Binary search algorithm.

Binary Search: Search a sorted array by repeatedly dividing the search interval in half. Begin with an interval covering the whole array. If the value of the search key is less than the item in the middle of the interval, narrow the interval to the lower half. Otherwise narrow it to the upper half. Repeatedly check until the value is found or the interval is empty.

GUI implementation steps :
1. Create a list of label according to the given list of numbers
2. Set their text, border, color and geometry with respective gap from each other
3. Each label height should be proportional to the value of each number
4. Create a start and pause push button to start the searching and pause the searching
5. Create a result label to show the searching status

Algorithm implementation steps :
1. Create label list corresponding to the given numbers
2. Create variable for the first last and mid index and flag for searching.
3. Add action to the push button, their action should change the flag status i.e start action should make flag true and pause action should make flag false
4. Create timer object which calls a method after every specific time
5. Inside the timer method check for the flag is flag is true begin the binary search algorithm
6. Calculate mid value and check if mid value is equal then stop the search and make label green.
7. Show result as found else change the value of first and last search according to the mid value. Make the label grey color and continue the search.
8. If the index of first become greater then index of last stop the search and show result as not found.

Below is the implementation –






# importing libraries
from PyQt5.QtWidgets import * 
from PyQt5 import QtCore, QtGui
from PyQt5.QtGui import * 
from PyQt5.QtCore import * 
import sys
  
  
class Window(QMainWindow):
  
    # list of numbers
    number = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 1213, 14, 15]
  
    def __init__(self):
        super().__init__()
  
        # setting title
        self.setWindowTitle("Binary search ")
  
        # setting geometry
        self.setGeometry(100, 100, 600, 400)
  
        # calling method
        self.UiComponents()
  
        # showing all the widgets
        self.show()
  
    # method for widgets
    def UiComponents(self):
  
        # start flag
        self.start = False
  
        # list to hold labels
        self.label_list = []
  
        # desired value
        self.desired = 9
  
        # binary search variable
        self.first = 0
        self.last = len(self.number) - 1
        self.mid = 0
  
        # local counter
        c = 0
  
        # iterating list of numbers
        for i in self.number:
  
            # creating label for each number
            label = QLabel(str(i), self)
  
            # adding background color and border
            label.setStyleSheet("border : 1px solid black; 
                                 background : white;")
  
            # aligning the text
            label.setAlignment(Qt.AlignTop)
  
            # setting geometry using local counter
            # first parameter is distance from left and 
            # second is distance from top
            # third is width and forth is height
            label.setGeometry(50 + c * 30, 50, 20, i * 10 + 10)
  
            # adding label to the label list
            self.label_list.append(label)
  
            # incrementing local counter
            c = c + 1
  
  
        # creating push button to start the search
        self.search_button = QPushButton("Start Search", self)
  
        # setting geometry of the button
        self.search_button.setGeometry(100, 270, 100, 30)
  
        # adding action to the search button
        self.search_button.clicked.connect(self.search_action)
  
        # creating push button to pause the search
        pause_button = QPushButton("Pause", self)
  
        # setting geometry of the button
        pause_button.setGeometry(100, 320, 100, 30)
  
        # adding action to the search button
        pause_button.clicked.connect(self.pause_action)
  
        # creating label to show the result
        self.result = QLabel("To search : " + str(self.desired), self)
  
        # setting geometry
        self.result.setGeometry(350, 280, 200, 40)
  
        # setting style sheet
        self.result.setStyleSheet("border : 3px solid black;")
  
        # adding font
        self.result.setFont(QFont('Times', 10))
  
        # setting alignment
        self.result.setAlignment(Qt.AlignCenter)
  
        # creating a timer object
        timer = QTimer(self)
  
        # adding action to timer
        timer.timeout.connect(self.showTime)
  
        # update the timer every 300 millisecond
        timer.start(300)
  
    # method called by timer
    def showTime(self):
  
  
        # checking if flag is true
        if self.start:
            # implementing binary search
            # finding mid index
            self.mid = (self.first + self.last)//2
  
            # if first index become greater than last index
            if self.first > self.last:
  
                # make start flag false
                self.start = False
                # show output as not found
                self.result.setText("Not Found")
  
            # if mid value is equal to the desired value
            if self.number[self.mid] == self.desired:
  
                # make flag false
                self.start = False
  
                # show output in result label
                self.result.setText("Found at index : " + str(self.mid))
  
                # set color of label to green
                self.label_list[self.mid].setStyleSheet(
                              "border : 2px solid green; "
                              "background-color : lightgreen")
  
            # if not equal to mid value
            else:
                # make color grey
                self.label_list[self.mid].setStyleSheet(
                                   "border : 1px solid black; "
                                   "background-color : grey")
  
            # mid value is higher
            if self.number[self.mid] > self.desired:
                # change last index
                self.last = self.mid - 1
  
            # if mid value is smaller
            if self.number[self.mid] < self.desired:
                # change first index
                self.first = self.mid + 1
  
  
  
    # method called by search button
    def search_action(self):
  
        # making flag true
        self.start = True
  
        # showing text in result label
        self.result.setText("Started searching...")
  
    # method called by pause button
    def pause_action(self):
  
        # making flag false
        self.start = False
  
        # showing text in result label
        self.result.setText("Paused")
  
  
# create pyqt5 app
App = QApplication(sys.argv)
  
# create the instance of our Window
window = Window()
  
# start the app
sys.exit(App.exec())

Output :

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