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.

已开始忘了考虑以空格结尾的串

public class Solution {
    public int lengthOfLastWord(String s) {
		// Start typing your Java solution below
		// DO NOT write main() function
		int len = s.length();
		boolean last_word = false;
		int last_word_pos = len - 1;
		for(int i = len - 1; i >= 0 ; i--){
			if(!last_word && s.charAt(i) != ' '){
				last_word = true;
				last_word_pos = i;
			}
			if(last_word && s.charAt(i) == ' ')
				return last_word_pos - i;
			if(last_word && i == 0)// s.charAt(i) != ' '
				return last_word_pos + 1;
			if(!last_word && i == 0)
				return 0;
		}
		return 0;
	}
}

public class Solution {
    public int lengthOfLastWord(String s) {
		// Start typing your Java solution below
		// DO NOT write main() function
		if (s.length() == 0)
			return 0;
		int i = s.length() - 1;
		int count = 0;
		while (i >= 0 && s.charAt(i) == ' ')
			--i;
		if (i == -1)
			return 0;
		while (i >= 0 && s.charAt(i) != ' ') {
			++count;
			--i;
		}
		return count;
	}
}