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(string s) {       int last_space = -1;       for(int i = 0 ; i< s.size() ; ++i){           if(s[i]==' ')            last_space = i;       }       if(last_space == -1)            return s.size();        else if(last_space == s.size() - 1){            int last_word = last_space  - 1;            while(last_word>=0&&s[last_word]==' ')                --last_word;            int count = 0;            while(last_word>=0&&s[last_word]!=' '){                ++count;                --last_word;            }            return count;        }        else            return s.size() - 1 - last_space;    }};