[📝LeetCode #58] Length of Last Word

🎀 The Problem

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

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

Example:

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

👩‍💻 My Answer

class Solution {
    public int lengthOfLastWord(String s) {
        boolean check = true;
        int count = 0;

        for (int i = 0; i < s.length(); i++) {
            char letter = s.charAt(i);
            if (check && letter != ' ')
                count++;
            else if  (!check && letter != ' ') {
                count = 1;
                check = true;
            }
            else
                check = false;
        }

        return count;
    }
}

Pro & Con

• ✅ Memory
• ✖️ Runtime

💋 Ideal Answer

Approach

I read the solution post on LeetCode and found it is better to iterate backward because we are looking for the LAST word.

New Code

class Solution {
    public int lengthOfLastWord(String s) {
        int count = 0;

        for (int i = s.length() - 1; i >= 0; i--) {
            char letter = s.charAt(i);
            if (letter != ' ') {
                count++;
            } else if  (count != 0 && letter == ' ')
                return count;
        }
        return count;
    }
}

💡 What I Learned

• Iterate backward!!! If you only care about the LAST word, iterate backward! The direction of iteration matters!

• ALSO! You don't need boolean to check. You can just use COUNTER (integer) of the letter. If its 0, then ' ' is just the one after the last word. If its more than 0, then ' ' is the one between the second last and last one!