Closed j0sh21 closed 1 month ago
Sure! Think of the backtracking algorithm as a smart way to solve problems where you have to make a series of choices, and some choices might lead to dead ends. It's like exploring a maze: you try a path, and if you hit a wall, you go back and try a different path.
Here's a simple step-by-step explanation:
Let's say we're solving a simple puzzle like a Sudoku. We fill in a number in an empty cell (choice), check if it fits with the rest of the puzzle (explore), and if it doesn't fit, we remove the number and try another one (backtrack).
Here's a basic Python example solving a simple problem: finding all possible ways to arrange numbers 1, 2, 3 in a sequence.
def backtrack(path, options):
if not options: # No more options to choose from
print(path) # We've found a valid sequence
return
for i in range(len(options)):
# Make a choice
next_option = options[i]
new_path = path + [next_option]
remaining_options = options[:i] + options[i+1:]
# Explore further with this choice
backtrack(new_path, remaining_options)
# No need to explicitly backtrack as we are using new lists
# Start with an empty path and all options available
backtrack([], [1, 2, 3])
In this example, the function backtrack
tries every possible arrangement of the numbers one, two, and three by making a choice, exploring further, and automatically backtracking by using new lists.
Does that make sense?
import requests from bs4 import BeautifulSoup from sqlalchemy import create_engine, Column, String, Integer, Float, Base from sqlalchemy.orm import sessionmaker
Base = declarative_base()
class OfficeListing(Base): tablename = 'office_listings' id = Column(Integer, primary_key=True, autoincrement=True) title = Column(String) price = Column(Float) address = Column(String) size = Column(String) url = Column(String)
engine = create_engine('sqlite:///office_listings.db') Base.metadata.create_all(engine) Session = sessionmaker(bind=engine) session = Session()
def scrape_immobilienscout24(): url = 'https://www.immobilienscout24.de/gewerbe-flaechen/de/nordrhein-westfalen/neuss-rhein-kreis/neuss/bu
Natürlich, hier ist ein vollständiger Prototyp einer Flask-App, die Echtzeit-Flugdaten für den Düsseldorf Airport und den Flughafen Mönchengladbach anzeigt.
Stelle sicher, dass du die notwendigen Python-Bibliotheken installiert hast:
pip install flask requests
Speichere den folgenden Code in einer Datei namens app.py
:
from flask import Flask, render_template_string
import requests
app = Flask(__name__)
# Replace with your actual FlightAware API credentials
FLIGHTAWARE_API_KEY = 'your_api_key_here'
BASE_URL = 'http://aviation-edge.com/v2/public/flights?key={api_key}&airportIata={airport_code}'
def get_flight_data(airport_code):
url = BASE_URL.format(api_key=FLIGHTAWARE_API_KEY, airport_code=airport_code)
response = requests.get(url)
return response.json()
@app.route('/')
def index():
dus_data = get_flight_data('DUS') # Düsseldorf Airport IATA code
mgb_data = get_flight_data('MGL') # Mönchengladbach Airport IATA code
template = '''
<!doctype html>
<html lang="en">
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1, shrink-to-fit=no">
<title>Flight Tracker</title>
</head>
<body>
<h1>Flight Tracker</h1>
<h2>Düsseldorf Airport (DUS)</h2>
<ul>
{% for flight in dus_data %}
<li>{{ flight['flight']['iataNumber'] }} - {{ flight['status'] }}</li>
{% endfor %}
</ul>
<h2>Mönchengladbach Airport (MGL)</h2>
<ul>
{% for flight in mgb_data %}
<li>{{ flight['flight']['iataNumber'] }} - {{ flight['status'] }}</li>
{% endfor %}
</ul>
</body>
</html>
'''
return render_template_string(template, dus_data=dus_data, mgb_data=mgb_data)
if __name__ == '__main__':
app.run(debug=True)
index
-Funktion definiert und zeigt eine Liste von Flügen für beide Flughäfen.'your_api_key_here'
mit deinem tatsächlichen API-Schlüssel.python app.py
http://127.0.0.1:5000/
, um die Echtzeit-Flugdaten zu sehen.Du kannst dieses Grundgerüst weiter ausbauen, um zusätzliche Funktionen hinzuzufügen oder das Layout zu verbessern. Viel Erfolg bei deinem Projekt!
import smtplib from email.mime.multipart import MIMEMultipart from email.mime.text import MIMEText import json
email_template = '''{ "to": "umweltamt@stadt.neuss.de", "subject": "Anfrage zur aktuellen Süßwasserqualität des Sees in Neuss", "body": "Sehr geehrte Damen und Herren,\n\nich hoffe, Sie können mir weiterhelfen. Ich möchte mich nach der aktuellen Süßwasserqualität des Sees in Neuss erkundigen. Könnten Sie mir bitte Informationen über die neuesten Wasseranalysen und die allgemeine Wasserqualität des Sees zur Verfügung stellen?\n\nVielen Dank im Voraus für Ihre Unterstützung." }'''
email_data = json.loads(email_template)
from_address = "deine.email@domain.de" to_address = email_data['to'] subject = email_data['subject'] body = email_data['body']
smtp_server = "smtp.your-email-provider.com" smtp_port = 587 smtp_username = "deine.email@domain.de" smtp_password = "deinpasswort"
msg = MIMEMultipart() msg['From'] = from_address msg['To'] = to_address msg['Subject'] = subject msg.attach(MIMEText(body, 'plain'))
try: server = smtplib.SMTP(smtp_server, smtp_port) server.starttls() server.login(smtp_username, smtp_password) server.send_message(msg) server.quit() print("E-Mail erfolgreich gesendet!") except Exception as e: print(f"Fehler beim Senden der E-Mail: {e}")
done
Sure, let's go through the code example row by row:
is_valid
Functionis_valid
function which checks if placingnum
inboard[row][col]
is valid according to Sudoku rules.num
is already in the row.num
is already in the column.num
is present. If it is, returnsFalse
.num
is not found in the row, column, or subgrid, returnsTrue
.solve_sudoku
Functionsolve_sudoku
function which attempts to solve the Sudoku puzzle using backtracking.0
).is_valid
to check if placingnum
in the current cell is valid.num
in the cell (makes a choice).solve_sudoku
to solve the rest of the board.True
, the puzzle is solved, so returnsTrue
.num
doesn't lead to a solution, resets the cell to zero (backtracks).False
to trigger backtracking.True
.Example Sudoku Board and Solving
0
).solve_sudoku
function to solve the puzzle.This code uses backtracking to try every possible number in each empty cell, backtracking whenever a number leads to an invalid state, until the entire board is correctly filled.
Does this step-by-step explanation help you understand how the code works?