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.

Code:

 1 int lengthOfLastWord(string s) {
 2         int temp = 0;
 3         bool flag = false;//flag为真表示已经找到最后一个有效字符
 4         for (int i = s.length()-1; i >= 0; --i)
 5         {
 6             if ( flag == false && s[i] != ' ')
 7             {
 8                 flag = true;
 9                 temp = i;
10                 continue;
11             }
12             if ( s[i] == ' ' && flag == true)
13                     return temp - i;
14         }
15         
16         if (flag == false)//全为空格
17             return 0;
18         return temp - i;//字符串中没有空格