[leedcode 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.

public class Solution {
    public int lengthOfLastWord(String s) {
        int res=0;
        int flag=0;
        //解题思路：flag代表后面是否出现过非空格的字符，当flag=1代表后面出现非空格，并且该字符为空格时，遍历结束
        
       /* for(int i=s.length()-1;i>=0;i--){
            if(s.charAt(i)!=' '){
                res++;
                flag=1;
            }else if(flag==1&&s.charAt(i)==' ')
                   break;
        }
        return res;*/
        //////////////第二种方式，先排除最后一位是空格的情况，本题题意“a ”应该返回1
        int i=s.length()-1;
        while(i>=0){
            if(s.charAt(i)!=' ')
               break;
              i--;
               
        }
        for(;i>=0;i--){
            if(s.charAt(i)==' ')
                 return res;
            else if(s.charAt(i)!=' '){
                res++;
            }
        }
        return res;
    }
}