Length of Last Word

来源：Leetcode

原帖：http://oj.leetcode.com/problems/length-of-last-word/

题目：
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.

代码：

 class Solution {  
 public:  
   int lengthOfLastWord(const char *s) {  
     if (*s == '\0' || s == NULL) return 0;  
     int res = 0;  
     int length = strlen(s);  
     s += length - 1;  
     while (*s == ' ' && length >= 0) {  
       s--; length--;  
     }  
     while (length >= 0 && isalpha(*s--)) {  
       res++; length--;  
     }  
     return res;  
   }  
 };