58. Length of Last Word Leetcode Java

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.

Solution:

The solution is very straightforward, find the last non-space char, then find the next space or till -1. return the difference between the two index.

Time complexity: O(n)

  public int lengthOfLastWord(String s) {  
     if(s==null || s.length()==0) return 0;  
    int i=s.length()-1;  
    while(i>=0 && s.charAt(i)==' ') i--;  
    int j=i;  
    while(j>=0 && s.charAt(j)!=' ') j--;  
    return i-j;  
   }