58. Length of Last Word

Easy

Given a string s consisting of words and spaces, return the length of the last word in the string.

A word is a maximal substring¹ consisting of non-space characters only.

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.

Constraints:

• 1 <= s.length <= 104
• s consists of only English letters and spaces .
• There will be at least one word in s.

Solution:

To solve this problem, we can follow these steps:

1. Trim the String: Remove any leading or trailing spaces.
2. Split the String into Words: Use spaces as the delimiter to split the string into an array of words.
3. Find the Last Word: Get the last element of the resulting array.
4. Calculate the Length: Return the length of the last word.

Let's implement this solution in PHP: 58. Length of Last Word

<?php
// Example usage:
$s1 = "Hello World";
$s2 = "   fly me   to   the moon  ";
$s3 = "luffy is still joyboy";

echo lengthOfLastWord($s1); // Output: 5
echo lengthOfLastWord($s2); // Output: 4
echo lengthOfLastWord($s3); // Output: 6

?>

Explanation:

1. Trim the String: The trim function removes any leading and trailing whitespace from the string. This ensures that we don't have extra spaces affecting our word splitting.

2. Split the String: The explode function splits the string into an array of words using a space ' ' as the delimiter.

3. Get the Last Word: The end function moves the internal pointer of the array to its last element and returns its value, which is the last word in our case.

4. Calculate the Length: The strlen function returns the length of the string, which is the length of the last word.

Example Walkthrough:

• For s = "Hello World":

  • Trimmed string: "Hello World"
  • Words array: ["Hello", "World"]
  • Last word: "World"
  • Length of last word: 5

• For s = " fly me to the moon ":

  • Trimmed string: "fly me to the moon"
  • Words array: ["fly", "me", "to", "the", "moon"]
  • Last word: "moon"
  • Length of last word: 4

• For s = "luffy is still joyboy":

  • Trimmed string: "luffy is still joyboy"
  • Words array: ["luffy", "is", "still", "joyboy"]
  • Last word: "joyboy"
  • Length of last word: 6

This code handles the given constraints and ensures that we correctly find the length of the last word in any valid input string.

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1. Substring A substring is a contiguous non-empty sequence of characters within a string. ↩