[leetcode.com]算法题目 – 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.

 class Solution {
 public:
     int lengthOfLastWord(const char *s) {
         // Start typing your C/C++ solution below
         // DO NOT write int main() function
         int len = strlen(s);
         if(==len) return ;         int last = len;
         int first = ;
         while(last> && s[last-]==' '){
             last--;
         }
         while(first<last && s[first]==' '){
             first++;
         }
         if(==last) return ;         int i;
         for(i=last-;i>=first;i--){
             if(s[i]==' ')  break;
         }
         return (last-i-);
     }
 };

我的答案