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

class Solution {
public:
    int lengthOfLastWord(const char *s) {
        int sum=0;
        int left=0;
        int right=strlen(s)-1;
        while(s[left]==' ')left++;
        while(s[right]==' ')right--;
       for(int i=left;i<=right;i++)
       {
           if(s[i]==' ')sum=0;
           else sum++;
       }
        return sum;
    }
};