LeetCode Challenge: 58. Length of Last Word 🚀

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String manipulation is a common coding interview topic, and this question is a great example of handling substrings effectively. let us solve it LeetCode 58: Length of the last word Use simple methods.

🚀 Problem description

Given a string s It consists of single words and spaces and returns the length of the last word in the string.

• A word is defined as the largest substring consisting only of non-space characters.

💡 Example

Example 1

Input: s = "Hello World"  
Output: 5  
Explanation: The last word is "World" with length 5.

Example 2

Input: s = "fly me to the moon"  
Output: 4  
Explanation: The last word is "moon" with length 4.

Example 3

Input: s = "luffy is still joyboy"  
Output: 6
Explanation: The last word is "joyboy" with length 6.

🏆 JavaScript solution

This problem can be solved by trimming unnecessary spaces and effectively positioning the last word.

implement

var lengthOfLastWord = function(s) {
    const words = s.trim().split(' ');

    return words[words.length - 1].length;
};

🔍 How it works

1. Trim string:
   • Remove leading and trailing spaces using trim() to simplify the logic.
2. Split string:
   • use split(' ') Divide the string into single words based on spaces.
3. Get the last sentence:
   • Access the last element of the array (words[words.length - 1]) and return its length.

🔑 Complexity analysis

• > Time complexity: O(n) is the length of the string. Both trimming and splitting strings run in linear time.
• > Space complexity: O(n)because splitting creates an array of single words.

Alternative solution (without splitting)

For space efficiency, traverse the string backwards to find the last word:

var lengthOfLastWord = function(s) {
    let length = 0;
    let i = s.length - 1;

    // Skip trailing spaces
    while (i >= 0 && s[i] === ' ') {
        i--;
    }

    // Count characters of the last word
    while (i >= 0 && s[i] !== ' ') {
        length++;
        i--;
    }

    return length;
};

🔑 Complexity analysis (alternative solutions)

• > Time complexity: O(n)when we iterate through the string once.
• > Space complexity: O(1)because no additional data structures are used.

📋 Run on empty

enter: s = "fly me to the moon"

Output: 4

✨ Professional tips for interviews

1. Explicit restrictions:

   • Can the string be empty?
   • Are there multiple spaces between words?

2. Optimize for edge cases:

   • Enter only spaces (" " → 0).
   • Single word input ("hello" → 5).

📚 Learn more

Check out the full explanation and code walkthrough on my Dev.to post:
👉 length of last word – JavaScript solution

How would you solve this problem? Let’s discuss it! 🚀