leetcode-Length of Last Word

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.

思路：双指针

代码：

int lengthOfLastWord(const char *s) {
        int len=strlen(s);
int p=len-1;
while(p>=0 && s[p]==' ')
{
--p;
}
int q=p;
while(q>=0 && s[q]!=' ')
{
--q;
}
return p-q;
    }