58.md

58. Length of Last Word

Description

Given a string s consists of upper/lower-case alphabets and empty space characters ' ', return the length of last word in the string.

If the last word does not exist, return 0.

Note: A word is defined as a character sequence consists of non-space characters only.

For example, Given s = "Hello World", return 5.

Thinking Process

1. This is a trivial question
2. Scan from the back of the list, keep a boolean value indicating if the count has start
3. End the loop if we see another ' ' after the count has started

Code

public class Solution {
    public int lengthOfLastWord(String s) {
        int len = 0;
        boolean startCounting = false;
        for(int i = s.length() - 1; i >=0 ; i--){
            if(startCounting){
                if(s.charAt(i) == ' ')
                    return len;
                else
                    len++;
            }else{
                if(s.charAt(i) == ' ')
                    continue;
                else{
                    startCounting = true;
                    len++;
                }
            }
        }
        return len;
    }
}

Complexity

1. O(n) time complexity as the string is scanned once