String Transforms Into Another String

The problem is asking us to determine if we can transform one string into another by repeatedly converting all occurrences of one character into another. Here’s the code that defines a solution:

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class Solution:
    def canConvert(self, str1: str, str2: str) -> bool:
        # If str1 is equal to str2, we don't need any conversion
        if str1 == str2:
            return True

        # Create a mapping to keep track of the transformations
        mapping = {}
        for c1, c2 in zip(str1, str2):
            # Check if we have seen a different transformation for this character before
            if c1 in mapping and mapping[c1] != c2:
                return False
            mapping[c1] = c2

        # If all characters in str2 are used, then we need an extra unused character to perform the transformation
        return len(set(str2)) < 26

Explanation:

If str1 and str2 are equal, we return True as no transformation is needed.
We use a mapping to record the transformation for each character in str1 to str2. If we find any conflicting transformation for the same character, we return False.
Finally, if all 26 characters are used in str2, then we cannot find an intermediate unused character to perform the transformation, and we return False. Otherwise, we return True.

10 Prerequisite LeetCode Problems

“1153. String Transforms Into Another String” is about string transformation where each transformation consists of replacing one occurrence of one letter with another letter. Here are 10 problems to prepare:

205. Isomorphic Strings: You need to determine if two given strings are isomorphic, meaning the characters in one string can be replaced to get the second string.
49. Group Anagrams: This problem requires you to group anagrams together, which is related to string transformation.
76. Minimum Window Substring: In this problem, you need to find the smallest window in the first string that contains all the characters of the second string.
383. Ransom Note: This problem involves finding if a ransom note can be constructed from a magazine. You need to check if one string can be transformed to another given the constraints.
438. Find All Anagrams in a String: This problem asks you to find all anagrams in a string which will help you to get a better understanding of string manipulation and transformation.
242. Valid Anagram: This is a simpler problem that asks you to determine if two given strings are anagrams.
567. Permutation in String: In this problem, you need to check if one string contains a permutation of another string.
680. Valid Palindrome II: This problem asks if a given string can become a palindrome after removing at most one character.
647. Palindromic Substrings: This problem requires you to count the number of palindromic substrings in a given string.
696. Count Binary Substrings: This problem asks you to count the number of binary substrings without changing the order of the characters.

These problems should give you a good idea of how to handle string transformation and manipulation problems. After solving these problems, you should be well-prepared for “1153. String Transforms Into Another String”.

“String Transforms Into Another String” involves manipulating strings based on certain conditions and transformations. It’s a good idea to tackle simpler problems that involve string manipulation, graph theory, and breadth-first search to gain a strong understanding of the underlying concepts. Here are 10 LeetCode problems that you should solve before this problem:

Find the Difference: This problem requires finding the difference between two strings.
Word Ladder: This problem involves transforming one word into another by changing only one letter at a time. It requires an understanding of breadth-first search, which is a common technique in transformation problems.
Course Schedule: This problem introduces graph theory and the concept of a cycle in a directed graph, which is an important concept to understand for the “String Transforms Into Another String” problem.
Course Schedule II: This problem extends the previous one by requiring you to return one correct ordering of courses.
Number of Islands: Although this problem isn’t about strings, it does involve understanding connected components in a grid which is an important graph theory concept.
Reconstruct Itinerary: This problem requires understanding of graph traversal to solve a problem involving string transformations.
Find and Replace Pattern: In this problem, you have to find all the words in a given list that follow a specific pattern, which will help in understanding transformation patterns between strings.

All these problems are relatively simpler than “String Transforms Into Another String” and are intended to build up the skills required to tackle this problem.

Problem Classification

Problem Statement:Given two strings str1 and str2 of the same length, determine whether you can transform str1 into str2 by doing zero or more conversions. In one conversion you can convert all occurrences of one character in str1 to any other lowercase English character. Return true if and only if you can transform str1 into str2.

Example 1:

Input: str1 = “aabcc”, str2 = “ccdee” Output: true Explanation: Convert ‘c’ to ’e’ then ‘b’ to ’d’ then ‘a’ to ‘c’. Note that the order of conversions matter. Example 2:

Input: str1 = “leetcode”, str2 = “codeleet” Output: false Explanation: There is no way to transform str1 to str2.

Constraints:

1 <= str1.length == str2.length <= 104 str1 and str2 contain only lowercase English letters.

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.

Distilling the Problem to Its Core Elements

In order to have me distill a problem to its core, you could ask questions that prompt for a deeper analysis of the problem, understanding of the underlying concepts, and simplification of the problem’s essence. Here are some examples of such prompts:

Can you identify the fundamental concept or principle this problem is based upon? Please explain.
What is the simplest way you would describe this problem to someone unfamiliar with the subject?
What is the core problem we are trying to solve? Can we simplify the problem statement?
Can you break down the problem into its key components?
What is the minimal set of operations we need to perform to solve this problem?

These prompts guide the discussion towards simplifying the problem, stripping it down to its essential elements, and understanding the core problem to be solved.

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.

Provide names by categorizing these cases

What are the key insights from analyzing the different cases?

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 ?

Could you please provide a stepwise refinement of our approach to solving this problem?
How can we take the high-level solution approach and distill it into more granular, actionable steps?
Could you identify any parts of the problem that can be solved independently?
Are there any repeatable patterns within our solution?

Solution Approach and Analysis

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?

Code Explanation and Design Decisions

Identify the initial parameters and explain their significance in the context of the problem statement or the solution domain.
Discuss the primary loop or iteration over the input data. What does each iteration represent in terms of the problem you’re trying to solve? How does the iteration advance or contribute to the solution?
If there are conditions or branches within the loop, what do these conditions signify? Explain the logical reasoning behind the branching in the context of the problem’s constraints or requirements.
If there are updates or modifications to parameters within the loop, clarify why these changes are necessary. How do these modifications reflect changes in the state of the solution or the constraints of the problem?
Describe any invariant that’s maintained throughout the code, and explain how it helps meet the problem’s constraints or objectives.
Discuss the significance of the final output in relation to the problem statement or solution domain. What does it represent and how does it satisfy the problem’s requirements?

Remember, the focus here is not to explain what the code does on a syntactic level, but to communicate the intent and rationale behind the code in the context of the problem being solved.

Coding Constructs

Consider the following piece of complex software code.

What are the high-level problem-solving strategies or techniques being used by this code?
If you had to explain the purpose of this code to a non-programmer, what would you say?
Can you identify the logical elements or constructs used in this code, independent of any programming language?
Could you describe the algorithmic approach used by this code in plain English?
What are the key steps or operations this code is performing on the input data, and why?
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.

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.
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.
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.

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.
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.
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.