58. 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.

 求最后一个单词的长度，要去掉最后多余的空格

C++（3ms）：

class Solution {
public:
    int lengthOfLastWord(string s) {
        int len = s.length() ;
        int res = 0 ;
        int tail = len-1 ;
        while(tail >= 0 && s[tail] == ' ')
            tail-- ;
        while(tail >= 0 && s[tail] != ' '){
            res++ ;
            tail-- ;
        }
        return res ;
    }
};

class Solution {
public:
    int lengthOfLastWord(string s) {
        int len = s.length() ;
        int res = 0 ;
        int i ;
        for (i = len-1 ; i >= 0  ; i--){
            if (s[i] != ' ')
                break ;
        }
        for(; i >= 0  ; i--){
            if (s[i] == ' ')
                break ;
            else
                res++ ;
        }
        return res ;
    }
};