[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(0==len) return 0;
        
        int last = len;
        int first = 0;
        while(last>0 && s[last-1]==' '){
            last--;
        }
        while(first<last && s[first]==' '){
            first++;
        }
        if(0==last) return 0;
        
        int i;
        for(i=last-1;i>=first;i--){
            if(s[i]==' ')  break;
        }
        return (last-i-1);
    }
};