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
class Solution:
     def lengthOfLastWord(self, s):
         """
         :type s: str
         :rtype: int
         """
         ans,tail=0,len(s)-1
         while tail>=0 and s[tail]==' ':
             tail-=1
         while tail>=0 and s[tail]!=' ':
             ans+=1
             tail-=1
         return ans
class Solution:
     def lengthOfLastWord(self, s):
         """
         :type s: str
         :rtype: int
         """
         ans,tail=0,len(s)-1
         while tail>=0 and s[tail]==' ':
             tail-=1
         while tail>=0 and s[tail]!=' ':
             ans+=1
             tail-=1
         return ans