Programming

Hello, In this article we’re going to explore the Method Injection and Property Injection design patterns. To demonstrate the patterns I’m going to add a new interface named Encoder to the printer.py file and a concrete implementation for two encoders: Rot13Encoder and NullEncoder. 1 2 3 4 5 6 7 8 9 10 11 12 13 class Encoder(metaclass=abc.ABCMeta): def encode(self, message: Message) -> Message: raise NotImplementedError("encode must be implemented!") class Rot13Encoder(metaclass=abc.ABCMeta): def encode(self, message: Message) -> Message: return Message(codecs.encode(str(message), 'rot_13')) class NullEncoder(metaclass=abc.ABCMeta): def encode(self, message: Message) -> Message: return message The Encoder will be used by the printer in order to encode the messages before printing them. ...

Hi, In this article I will explain my solution for the following LeetCode problem: Reverse Linked List. If you’re interested in solving this problem then please try to spend at least one hour or more on it before looking at my solution. To help you solve this problem I’ve created the following table: Current Prev 1 NULL 2 1 3 2 NULL 3 Think about how you can use this table to write an iterative or recursive algorithm that reverses the linked list. ...

The Constructor Injection design pattern is a pattern that helps you declare all the required dependencies of a class in it’s constructor. This is useful because it helps you decouple the code, you can specify an interface instead of a concrete type, remember, program to an interface. Also, in the constructor it is easier to guard against null objects. The calling code doesn’t have to worry about null exceptions every time it uses a dependency. ...

The composition root is a design pattern which helps you structure a software application by implementing a class that builds all the other classes. In this example we will examine this pattern in Python. Here’s the object graph of the classes that we’re going to implement: I have designed a sample application that we’re going to use. It contains three components: ConsoleInputListener, ConsolePrinter and RomanianTranslator and a value object class: Message. ...

Hello, Here’s my solution for the flood fill problem, found on LeetCode. If you want me to write about certain topics please let me know in the comments, thank you! Link to the problem: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 """ An image is represented by a 2-D array of integers, each integer representing the pixel value of the image (from 0 to 65535). Given a coordinate (sr, sc) representing the starting pixel (row and column) of the flood fill, and a pixel value newColor, "flood fill" the image. To perform a "flood fill", consider the starting pixel, plus any pixels connected 4-directionally to the starting pixel of the same color as the starting pixel, plus any pixels connected 4-directionally to those pixels (also with the same color as the starting pixel), and so on. Replace the color of all of the aforementioned pixels with the newColor. At the end, return the modified image. """ from typing import List, Tuple class Solution: def __init__(self): self.visited = set() def _set_pixel(self, image: List[List[int]], point: Tuple[int, int], value: int): try: image[point[0]][point[1]] = value except IndexError: pass def _get_pixel(self, image: List[List[int]], point: Tuple[int, int]): if point[0] < 0 or point[1] < 0: return None try: return image[point[0]][point[1]] except IndexError: return None def _floodFill(self, image: List[List[int]], point: Tuple[int, int], color: int, newColor: int) -> List[List[int]]: pixel = self._get_pixel(image, point) if pixel is not None and pixel == color and point not in self.visited: self.visited.add(point) self._set_pixel(image, point, newColor) self._floodFill(image, (point[0], point[1] + 1), color, newColor) self._floodFill(image, (point[0], point[1] - 1), color, newColor) self._floodFill(image, (point[0] + 1, point[1]), color, newColor) self._floodFill(image, (point[0] - 1, point[1]), color, newColor) def floodFill(self, image: List[List[int]], sr: int, sc: int, newColor: int) -> List[List[int]]: point = (sr, sc) pixel = self._get_pixel(image, point) self.visited = set() if pixel is not None: self._floodFill(image, point, pixel, newColor) return image if __name__ == '__main__': s = Solution() out = s.floodFill([[1,1,1],[1,1,0],[1,0,1]], 1, 1, 2) print("Output", out) assert out == [[2,2,2],[2,2,0],[2,0,1]] out = s.floodFill([[0,0,0],[0,0,0]], 0, 0, 2) print("Output", out) assert out == [[2,2,2],[2,2,2]] out = s.floodFill([[0,0,0],[0,1,1]], 1, 1, 1) print("Output", out) assert out == [[0, 0, 0], [0, 1, 1]]

Hello, In this article I will introduce you to pyenv, a tool for managing python environments. Installing pyenv is pretty straight forward, you’ll need to clone the repo and add the binaries to the path. For a typical Debian based distro using the Zsh shell the instructions would be: 1 2 3 4 git clone https://github.com/pyenv/pyenv.git ~/.pyenv echo 'export PYENV_ROOT="$HOME/.pyenv"' >> ~/.zshrc echo 'export PATH="$PYENV_ROOT/bin:$PATH"' >> ~/.zshrc Then, in order for this to take effect, you need to reload the shell with: source ~/.zshrc, or just restart your terminal. 😀 ...

Hello In this article I will present you my Python3 solution for the following problem which I found on LeetCode: find-the-town-judge. Note: The solution is on the second page, so you won’t get spoiled if you want to attempt to solve the problem by yourself. Have fun! 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 from collections import defaultdict from typing import List """ In a town, there are N people labelled from 1 to N. There is a rumor that one of these people is secretly the town judge. If the town judge exists, then: The town judge trusts nobody. Everybody (except for the town judge) trusts the town judge. There is exactly one person that satisfies properties 1 and 2. You are given trust, an array of pairs trust[i] = [a, b] representing that the person labelled a trusts the person labelled b. If the town judge exists and can be identified, return the label of the town judge. Otherwise, return -1. """ class Solution: def _filterForJudge(self, N, trust_dict): no_trustees = None for i in range(1, N + 1): person_trusted = trust_dict.get(i, set()) if len(person_trusted) == 0: if no_trustees is None: no_trustees = i else: return None return no_trustees def findJudge(self, N: int, trust: List[List[int]]) -> int: trust_dict = defaultdict(set) for i in trust: trust_dict[i[0]].add(i[1]) # The town judge trusts nobody. no_trustee = self._filterForJudge(N, trust_dict) if no_trustee: # Everybody trusts the town judge. people_who_trust = 0 for p in trust_dict.items(): # Check if the person trusts the town judge. if no_trustee in p[1]: people_who_trust += 1 if people_who_trust == N-1: return no_trustee return -1 if __name__ == '__main__': s = Solution() print(s.findJudge(2, [[1,2]])) print(s.findJudge(3, [[1,3],[2,3]])) print(s.findJudge(3, [[1,3],[2,3],[3,1]])) print(s.findJudge(3, [[1,2],[2,3]])) print(s.findJudge(4, [[1,3],[1,4],[2,3],[2,4],[4,3]])) Thanks for reading! ...

Hello, Here are my solutions for the second part of the card: Arrays 101, from LeetCode. Duplicate Zeroes Given an array of integers, remove duplicate zeroes and shift the remaining elements. 1 2 3 4 5 6 7 8 9 10 11 12 13 class Solution: def duplicateZeros(self, arr: List[int]) -> None: """ Do not return anything, modify arr in-place instead. """ index = 0 arr_length = len(arr) while index < arr_length: if arr[index] == 0: arr.insert(index, 0) arr.pop() index += 1 index += 1 Merge Sorted Array Given two sorted arrays, merge them together into nums1. ...

Hello, LeetCode is a good place to practice programming by solving problems of all levels! After you solve a problem, you’ll get access to all submitted solutions, sorted by time and memory usage. That’s a nice way to compare your code to others and see what you did well and where you can improve. Here’s my solutions for the Arrays 101: Introduction card: Max Consecutive Ones 1 2 3 4 5 6 7 8 9 10 11 12 13 14 class Solution: def findMaxConsecutiveOnes(self, nums: List[int]) -> int: max_counter = 0 counter = 0 for i in nums: if i == 1: counter += 1 else: if counter > max_counter: max_counter = counter counter = 0 if counter > max_counter: max_counter = counter return max_counter Find Numbers with Even Number of Digits 1 2 3 4 5 6 7 8 9 10 11 12 class Solution: @staticmethod def is_even(value): return len(str(value)) % 2 == 0 def findNumbers(self, nums: List[int]) -> int: return_value = 0 for number in nums: if self.is_even(number): return_value += 1 return return_value Squares of a Sorted Array When writing code like this be careful because you’re altering the A list in place. ...

Hello, I’m still working on my NucuCar project from time to time, I’m currently at my parents home and I left the raspberry pi at my apartment so I’m only testing the builds it on my computer. Luckily I can test the telemetry by using the CPU temperature sensor implemented by dotnet IoT. For the next step, I wanted an effective way to store telemetry data in the cloud, preferably for free, since this is a hobby project after all. ...