058-length-of-last-word

Question

https://leetcode.com/problems/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.

Example:

Input: "Hello World"
Output: 5

Thought Process

1. Scanning Backward
   1. Having a pointer points at the end of the string and move forward the string if it's a space
   2. Then we stop at the end of the last word
   3. Increase the length as long as the character is not a space
   4. Time complexity O(n)
   5. Space complexity O(1)

Solution

class Solution {
    public int lengthOfLastWord(String s) {
        int len = 0, tail = s.length() - 1;
        while(tail >= 0 && s.charAt(tail) == ' ') tail--;
        while(tail >= 0 && s.charAt(tail) != ' '){
            len++;
            tail--;
        }
        return len;
    }
}

Additional