[leetcode]Length of Last Word

class Solution {public:    int lengthOfLastWord(const char *s) {        // Start typing your C/C++ solution below        // DO NOT write int main() function        int N = 0;        const char *p = s;        while(*p){            p++;            N++;        }                int i = N-1;        while(i >= 0 && s[i] == ' '){            i--;        }        if(i == -1) return 0;        int end = i;                while(i >= 0 && s[i] != ' '){            i--;        }        int start = i;                return end-start;            }};