Design a Text Editor

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class TextEditor:
    def __init__(self):
        self.text = []
        self.cursor = 0

    def addText(self, text: str) -> None:
        self.text[self.cursor:self.cursor] = text
        self.cursor += len(text)

    def deleteText(self, k: int) -> int:
        chars_deleted = min(k, self.cursor)
        self.text[self.cursor - chars_deleted:self.cursor] = []
        self.cursor -= chars_deleted
        return chars_deleted

    def cursorLeft(self, k: int) -> str:
        self.cursor = max(0, self.cursor - k)
        return ''.join(self.text[max(0, self.cursor - 10):self.cursor])

    def cursorRight(self, k: int) -> str:
        self.cursor = min(len(self.text), self.cursor + k)
        return ''.join(self.text[max(0, self.cursor - 10):self.cursor])

Explanation:

  1. self.text maintains the current text as a list of characters to allow efficient insertion and deletion.
  2. self.cursor keeps track of the cursor position within the text.
  3. addText appends the provided text to where the cursor is.
  4. deleteText deletes k characters to the left of the cursor.
  5. cursorLeft and cursorRight move the cursor to the left or right k times. They also return the last min(10, len) characters to the left of the cursor.

The given constraints and example inputs should work well with this implementation.

Identifying Problem Isomorphism

“Design a Text Editor” is linked to “Basic Calculator II”. Both involve the processing and manipulation of strings, although the two are approximately isomorphic.

“Design a Text Editor” is a problem where you have to implement various operations of a text editor such as inserting characters, deleting characters, undoing operations, and so on. It’s about designing a system that can efficiently perform these operations and manage the state of the text.

“Basic Calculator II” involves implementing a basic calculator to evaluate a simple expression string that contains only non-negative integers, +, -, *, / operators, and empty spaces. The integer division should truncate toward zero.

Both problems deal with the manipulation of strings and managing operations on them. “Basic Calculator II” is simpler because it’s about calculating a mathematical expression. “Design a Text Editor” is more complex as it involves designing various operations and managing the state of the text at all times. Being proficient with “Basic Calculator II” could serve as a starting point for understanding and handling the more intricate problem of “Design a Text Editor”.

10 Prerequisite LeetCode Problems

“Design a Text Editor” requires understanding of the data structures, algorithms, and design patterns that can be used to implement a basic text editor.

Here are 10 problems, listed in order of increasing difficulty:

  1. “Implement strStr()” (LeetCode Problem #28): This problem requires implementing a string search algorithm, which is a basic requirement in a text editor for search functionality.

  2. “Reverse String” (LeetCode Problem #344): This problem will familiarize you with manipulation of character arrays or strings which is a common task in a text editor.

  3. “Longest Common Prefix” (LeetCode Problem #14): Understanding how to compare and manipulate strings in this way will be helpful in designing a text editor.

  4. “Valid Palindrome” (LeetCode Problem #125): This problem requires you to consider alphanumeric characters and ignoring cases, which is necessary for certain text processing tasks in a text editor.

  5. “Backspace String Compare” (LeetCode Problem #844): A text editor should handle backspaces, and this problem provides practice with that.

  6. “Design Circular Deque” (LeetCode Problem #641): Understanding how to design a Double-Ended Queue can be useful in a text editor for implementing undo and redo functionality.

  7. “Basic Calculator II” (LeetCode Problem #227): This problem involves parsing and evaluating a string of text, similar to what a text editor might have to do in certain scenarios.

  8. “Longest Substring Without Repeating Characters” (LeetCode Problem #3): Manipulating substrings and dealing with character repetitions is a crucial part of text editor functionality.

  9. “Text Justification” (LeetCode Problem #68): Justifying text is an advanced feature that some text editors have, and this problem can help you practice implementing it.

  10. “Design Search Autocomplete System” (LeetCode Problem #642): Many text editors have autocomplete functionality. Designing a system for it can help you understand the considerations involved.

Designing a text editor can be a complex task depending on the level of functionality you want to include. It’s not just about manipulating strings, but also about handling user inputs, providing a user interface, managing memory, and potentially even networking if it’s a collaborative text editor.

Problem Classification

Problem Statement: Design a text editor with a cursor that can do the following: Add text to where the cursor is. Delete text from where the cursor is (simulating the backspace key). Move the cursor either left or right. When deleting text, only characters to the left of the cursor will be deleted. The cursor will also remain within the actual text and cannot be moved beyond it. More formally, we have that 0 <= cursor.position <= currentText.length always holds.

Implement the TextEditor class: TextEditor() Initializes the object with empty text. void addText(string text) Appends text to where the cursor is. The cursor ends to the right of text. int deleteText(int k) Deletes k characters to the left of the cursor. Returns the number of characters actually deleted. string cursorLeft(int k) Moves the cursor to the left k times. Returns the last min(10, len) characters to the left of the cursor, where len is the number of characters to the left of the cursor. string cursorRight(int k) Moves the cursor to the right k times. Returns the last min(10, len) characters to the left of the cursor, where len is the number of characters to the left of the cursor.

Example 1:

Input [“TextEditor”, “addText”, “deleteText”, “addText”, “cursorRight”, “cursorLeft”, “deleteText”, “cursorLeft”, “cursorRight”] [[], [“leetcode”], [4], [“practice”], [3], [8], [10], [2], [6]] Output [null, null, 4, null, “etpractice”, “leet”, 4, “”, “practi”]

Explanation TextEditor textEditor = new TextEditor(); // The current text is “|”. (The ‘|’ character represents the cursor) textEditor.addText(“leetcode”); // The current text is “leetcode|”. textEditor.deleteText(4); // return 4 // The current text is “leet|”. // 4 characters were deleted. textEditor.addText(“practice”); // The current text is “leetpractice|”. textEditor.cursorRight(3); // return “etpractice” // The current text is “leetpractice|”. // The cursor cannot be moved beyond the actual text and thus did not move. // “etpractice” is the last 10 characters to the left of the cursor. textEditor.cursorLeft(8); // return “leet” // The current text is “leet|practice”. // “leet” is the last min(10, 4) = 4 characters to the left of the cursor. textEditor.deleteText(10); // return 4 // The current text is “|practice”. // Only 4 characters were deleted. textEditor.cursorLeft(2); // return "" // The current text is “|practice”. // The cursor cannot be moved beyond the actual text and thus did not move. // "" is the last min(10, 0) = 0 characters to the left of the cursor. textEditor.cursorRight(6); // return “practi” // The current text is “practi|ce”. // “practi” is the last min(10, 6) = 6 characters to the left of the cursor.

Constraints:

1 <= text.length, k <= 40 text consists of lowercase English letters. At most 2 * 104 calls in total will be made to addText, deleteText, cursorLeft and cursorRight. Follow-up: Could you find a solution with time complexity of O(k) per call?

Analyze the provided problem statement. Categorize it based on its domain, ignoring ‘How’ it might be solved. Identify and list out the ‘What’ components. Based on these, further classify the problem. Explain your categorizations.

Identifying Problem Isomorphism

Can you help me with finding the isomorphism for this problem?

Which problem does this problem map to the corresponding isomorphic problem on Leetcode ?

How did you identify that this problem is a variation of problem?

Visual Model of the Problem

How to visualize the problem statement for this problem?

Problem Restatement

Could you start by paraphrasing the problem statement in your own words? Try to distill the problem into its essential elements and make sure to clarify the requirements and constraints. This exercise should aid in understanding the problem better and aligning our thought process before jumping into solving it.

Abstract Representation of the Problem

Could you help me formulate an abstract representation of this problem?

Given this problem, how can we describe it in an abstract way that emphasizes the structure and key elements, without the specific real-world details?

Terminology

Are there any specialized terms, jargon, or technical concepts that are crucial to understanding this problem or solution? Could you define them and explain their role within the context of this problem?

Problem Simplification and Explanation

Could you please break down this problem into simpler terms? What are the key concepts involved and how do they interact? Can you also provide a metaphor or analogy to help me understand the problem better?

Constraints

Given the problem statement and the constraints provided, identify specific characteristics or conditions that can be exploited to our advantage in finding an efficient solution. Look for patterns or specific numerical ranges that could be useful in manipulating or interpreting the data.

What are the key insights from analyzing the constraints?

Case Analysis

Could you please provide additional examples or test cases that cover a wider range of the input space, including edge and boundary conditions? In doing so, could you also analyze each example to highlight different aspects of the problem, key constraints and potential pitfalls, as well as the reasoning behind the expected output for each case? This should help in generating key insights about the problem and ensuring the solution is robust and handles all possible scenarios.

Identification of Applicable Theoretical Concepts

Can you identify any mathematical or algorithmic concepts or properties that can be applied to simplify the problem or make it more manageable? Think about the nature of the operations or manipulations required by the problem statement. Are there existing theories, metrics, or methodologies in mathematics, computer science, or related fields that can be applied to calculate, measure, or perform these operations more effectively or efficiently?

Problem Breakdown and Solution Methodology

Given the problem statement, can you explain in detail how you would approach solving it? Please break down the process into smaller steps, illustrating how each step contributes to the overall solution. If applicable, consider using metaphors, analogies, or visual representations to make your explanation more intuitive. After explaining the process, can you also discuss how specific operations or changes in the problem’s parameters would affect the solution? Lastly, demonstrate the workings of your approach using one or more example cases.

Inference of Problem-Solving Approach from the Problem Statement

How did you infer from the problem statement that this problem can be solved using ?

Stepwise Refinement

  1. Could you please provide a stepwise refinement of our approach to solving this problem?

  2. How can we take the high-level solution approach and distill it into more granular, actionable steps?

  3. Could you identify any parts of the problem that can be solved independently?

  4. Are there any repeatable patterns within our solution?

Solution Approach and Analysis

Given the problem statement, can you explain in detail how you would approach solving it? Please break down the process into smaller steps, illustrating how each step contributes to the overall solution. If applicable, consider using metaphors, analogies, or visual representations to make your explanation more intuitive. After explaining the process, can you also discuss how specific operations or changes in the problem’s parameters would affect the solution? Lastly, demonstrate the workings of your approach using one or more example cases.

Thought Process

Explain the thought process by thinking step by step to solve this problem from the problem statement and code the final solution. Write code in Python3. What are the cues in the problem statement? What direction does it suggest in the approach to the problem? Generate insights about the problem statement.

From Brute Force to Optimal Solution

Could you please begin by illustrating a brute force solution for this problem? After detailing and discussing the inefficiencies of the brute force approach, could you then guide us through the process of optimizing this solution? Please explain each step towards optimization, discussing the reasoning behind each decision made, and how it improves upon the previous solution. Also, could you show how these optimizations impact the time and space complexity of our solution?

Coding Constructs

Consider the following piece of complex software code.

  1. What are the high-level problem-solving strategies or techniques being used by this code?

  2. If you had to explain the purpose of this code to a non-programmer, what would you say?

  3. Can you identify the logical elements or constructs used in this code, independent of any programming language?

  4. Could you describe the algorithmic approach used by this code in plain English?

  5. What are the key steps or operations this code is performing on the input data, and why?

  6. Can you identify the algorithmic patterns or strategies used by this code, irrespective of the specific programming language syntax?

Language Agnostic Coding Drills

Your mission is to deconstruct this code into the smallest possible learning units, each corresponding to a separate coding concept. Consider these concepts as unique coding drills that can be individually implemented and later assembled into the final solution.

  1. Dissect the code and identify each distinct concept it contains. Remember, this process should be language-agnostic and generally applicable to most modern programming languages.

  2. Once you’ve identified these coding concepts or drills, list them out in order of increasing difficulty. Provide a brief description of each concept and why it is classified at its particular difficulty level.

  3. Next, describe the problem-solving approach that would lead from the problem statement to the final solution. Think about how each of these coding drills contributes to the overall solution. Elucidate the step-by-step process involved in using these drills to solve the problem. Please refrain from writing any actual code; we’re focusing on understanding the process and strategy.

Targeted Drills in Python

Now that you’ve identified and ordered the coding concepts from a complex software code in the previous exercise, let’s focus on creating Python-based coding drills for each of those concepts.

  1. Begin by writing a separate piece of Python code that encapsulates each identified concept. These individual drills should illustrate how to implement each concept in Python. Please ensure that these are suitable even for those with a basic understanding of Python.

  2. In addition to the general concepts, identify and write coding drills for any problem-specific concepts that might be needed to create a solution. Describe why these drills are essential for our problem.

  3. Once all drills have been coded, describe how these pieces can be integrated together in the right order to solve the initial problem. Each drill should contribute to building up to the final solution.

Remember, the goal is to not only to write these drills but also to ensure that they can be cohesively assembled into one comprehensive solution.

Q&A

Similar Problems

Given the problem , identify and list down 10 similar problems on LeetCode. These should cover similar concepts or require similar problem-solving approaches as the provided problem. Please also give a brief reason as to why you think each problem is similar to the given problem.