Solving the Reverse Words in a String in Java (Leet code problem solving Part 2 )

In this series I'll be solving Leetcode problems for SDETs one by one.

Problem

557. Reverse Words in a String III

Given a string s, reverse the order of characters in each word within a sentence while still preserving whitespace and initial word order.

Example 1:

Input: s = "Let's take LeetCode contest" Output: "s'teL ekat edoCteeL tsetnoc"

Example 2:

Input: s = "Mr Ding" Output: "rM gniD"

Approach

The "Reverse Words in a String III" problem is a common coding challenge that falls under the category of string manipulation. The problem statement asks us to reverse the order of characters within each word in a given sentence while maintaining the original whitespace and word order. In this article, we will explore the problem, understand the provided Java solution, and delve into a detailed explanation of the code.

Input:

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s = "Let's take LeetCode contest"

Output:

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"s'teL ekat edoCteeL tsetnoc"

Explanation:

• The word "Let's" becomes "s'teL".
• The word "take" becomes "ekat".
• The word "LeetCode" becomes "edoCteeL".
• The word "contest" becomes "tsetnoc".
• The order of words is maintained, and whitespace is preserved.

Code:

Now, let's delve into the Java code that embodies this approach.

java Code :

public static void main(String[] args) {  
    System.out.println(reverseWords("Let's take LeetCode contest"));  
}  
  
public static String reverseWords(String s) {  
  
    String op = "";  
    for (String a : s.split("  ")) {  
        op += reverseString(a) + " ";  
        System.out.println(op);  
    }  
    return op.substring(0, s.length());  
}  
  
public static String reverseString(String s) {  
    char[] a = s.toCharArray();  
    String op = "";  
    for (int i = a.length-1; i >= 0; i--) {  
        op += a[i];  
    }  
    return op;  
}

Explanation of the Java Code:

1. The main method serves as the entry point, calling the reverseWords method with the provided input string.

2. The reverseWords method takes a string s as input and initializes an empty string op to store the output.

3. The code uses a for loop to iterate over each word in the input string, which is obtained by splitting the input string using whitespace as the delimiter (s.split(" ")).

4. For each word a, the code calls the reverseString method to reverse the characters in the word. The reversed word is then concatenated with a space to the op string.

5. Finally, the method returns a substring of op from index 0 to the length of the original input string s. This is done to remove the extra space added after the last word.

Using string builder

public String reverseWords(String s) {  
    String op = "";  
    for (String a : s.split("  ")) {  
        StringBuilder sb = new StringBuilder(a);  
        sb.reverse();  
        op += sb + " ";  
    }  
    return op.substring(0,s.length());  
}

Javascript :

function reverseWords(s) {
    // Split the input string into words
    const words = s.split(' ');

    // Reverse each word
    const reversedWords = words.map(word => {
        return word.split('').reverse().join('');
    });

    // Join the reversed words back into a sentence
    const result = reversedWords.join(' ');

    return result;
}

// Example usage:
const input1 = "Let's take LeetCode contest";
const output1 = reverseWords(input1);
console.log(output1); // Output: "s'teL ekat edoCteeL tsetnoc"

const input2 = "Mr Ding";
const output2 = reverseWords(input2);
console.log(output2); // Output: "rM gniD"

Code files : https://github.com/Bosco98/Practice/blob/main/src/RevWord.java

Entire repo : https://github.com/Bosco98/Practice/