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.

class Solution {
public:
    int lengthOfLastWord(const char *s) 
    {
        int count=0;
        int index=strlen(s)-1;
        while(index>=0 && s[index]==' ')
            index--;
        while(index>=0 && s[index]!=' ')
        {
            index--;
            count++;
        }
        
        //if(index==-1) return 0;
        return count;
    }
};