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.

Example:

Input: "Hello World"
Output: 5

 1 class Solution {
 2 public:
 3     int lengthOfLastWord(string s) {
 4         int idx = s.rfind(' ');
 5         if (idx == s.npos)
 6             return s.length();
 7         if (idx == s.length() - 1) {
 8             s.erase(s.length() - 1);
 9             return lengthOfLastWord(s);
10         }
11         return s.length() - idx - 1;
12     }
13 };

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主要需要细心，考虑问题全面