LeetCode--Length Of Last Word

class Solution {public:    int lengthOfLastWord(const char *s) {        const char *p = s;        if( p == NULL)            return 0;        int len = 0;        while( (*p) != '\0')        {            len ++;            p++;        }                int last_len = 0;        int flag = 0;        for(int i=len-1; i>=0; i--)        {            if(s[i] == ' ' && flag == 0)                ;            else if(s[i] == ' ' && flag == 1)                return last_len;            else            {                if( flag == 0 )                    flag = 1;                last_len++;            }        }                return last_len;            }};