[leetcode]58. Length of Last Word最后一个词的长度

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.

Example:

Input: "Hello World"
Output: 5

题意：

最后一个词的长度

Solution1： Just like do the simulation of  s.trim(). 

code

/*
Time: O(n). 
Space: O(1). 
*/
class Solution {
     public int lengthOfLastWord(String s) {
        // corner case
        if (s == null || s.length() == 0) return 0;
        int right = s.length() - 1;
        int i = 0;
        // 先把last word右边的空格扫清
        while (right > 0 && s.charAt(right) == ' ') right--;
        i = right;
        // 定住right, 用i来扫出last word的长度
        while (i >= 0 && s.charAt(i) != ' ') i--;
        return right - i;
    }    
}