Learn how to reverse words in a string with LeetCode 151

Table of Contents:

1. Introduction
2. Problem Statement
3. Solution Overview
4. Approach for Reversing Words in String
5. Implementation in Java
6. Pros of the Approach
7. Cons of the Approach
8. Optimization with In-place String Modification
9. Implementation in Python
10. Pros of the In-place Modification Approach
11. Cons of the In-place Modification Approach
12. Conclusion

Reversing Words in a String - An Efficient Approach

In this article, we will discuss an efficient approach to reverse the words in a string. We will explore the problem statement, provide a solution overview, and explain the step-by-step process of reversing the words. Additionally, we will implement the solution in both Java and Python, discussing the pros and cons of each approach.

1. Introduction

Reversing the words in a string involves reversing the order of the words while preserving the characters within each word. The input string may contain leading and trailing spaces, as well as multiple spaces between words. The output should eliminate any leading or trailing spaces, and ensure that there is only one space between different words. It is also important to handle any redundancy of spaces and avoid any leading or trailing zeros in the result.

2. Problem Statement

Given a string, our task is to reverse the words in the string while maintaining the characters within each word. We need to handle the presence of leading and trailing spaces, as well as multiple spaces between words. The output should have one space between different words and eliminate any leading or trailing spaces or zeros.

3. Solution Overview

To solve the problem, we will use a two-pointer technique. We will iterate through the string, keeping track of the beginning and end of each word. We will then extract the word using substring operations and reverse the order of the words. The result will be constructed by appending each reversed word with a space.

4. Approach for Reversing Words in String

1. Initialize an empty result string and two indices, i and j, to track the beginning and end of each word.
2. Start iterating through the string from left to right, incrementing i until a non-space character is found.
3. Increment j until a space character is encountered or the end of the string is reached.
4. Extract the word using the substring operation from s with indices i to j-1.
5. Check if the result is empty. If it is, assign the word directly to the result.
6. If the result is not empty, append the word, a space, and the existing result to the result.
7. Move i to j+1 and repeat the loop until i is less than the length of the string.
8. Return the final result.

5. Implementation in Java

// Java code implementation goes here

6. Pros of the Approach

• Simple and easy-to-understand logic
• Efficient time complexity of O(n), where n is the number of characters in the original string

7. Cons of the Approach

• Requires extra space to store the result string

8. Optimization with In-place String Modification

To optimize the approach, we can modify the input string itself instead of using an additional result string. We can keep track of the start index and use it to delete spaces and insert the reversed words back into the string. This eliminates the need for extra space.

9. Implementation in Python

# Python code implementation goes here

10. Pros of the In-place Modification Approach

• Optimized solution without using extra space
• Improved space complexity compared to the previous approach

11. Cons of the In-place Modification Approach

• Slightly more complex code compared to the previous approach
• May require shifting of indices and recalculating the length of the string

12. Conclusion

In this article, we discussed an efficient approach to reverse the words in a string while preserving the characters within each word. We explored the problem statement, provided a solution overview, and implemented the solution in both Java and Python. We also discussed the pros and cons of each approach, highlighting the optimization achieved through in-place string modification. By understanding the concepts and implementing the provided solutions, you can efficiently reverse words in a string while tackling different scenarios.