Length of Last Word | Leetcode

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.

两个下标，head搜索非空格元素，last搜索head后的第一个空格或者字符串结尾。检测到单词后保存至lastlen里。

class Solution {
public:
    int lengthOfLastWord(string s) {
        const unsigned int len = s.size();
        unsigned int head,last,lastlen;
        head = ;
        last = ;
        lastlen = ;
        if (!len)
            ;
        )    {
            // search for the first non-space character
            while ((s[head] == ' ') && (head != len))
                head ++;
            if (head == len)
                return lastlen;
            last = head；
            while ((last != len) && (s[last] != ' '))
                last ++;
            if (last == len)
                return last - head;
            else    {
                lastlen = last - head;
                head = last;
            }
        }
    }
};