leetcode : Length of Last Word [基本功]

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.

 

思路： 两根指针

（1） 先从右往左判断是否有空

（2）移动左指针

（3） 右指针 - 左指针

 

public class Solution {
    public int lengthOfLastWord(String s) {
        if(s == null || s.length() == 0) {
            return 0;
        }
        int start = 0;
        int end = s.length() - 1;
        
        while(end >= 0 && s.charAt(end) == ' ') {
            end --;
        }
        
        start = end;
        
        while(start >= 0 && s.charAt(start) != ' ') {
            start--;
        }
        return end - start ;
    }
}