# Length of Last Word ### Source - leetcode: [Length of Last Word | LeetCode OJ](https://leetcode.com/problems/length-of-last-word/) - lintcode: [(422) Length of Last Word](http://www.lintcode.com/en/problem/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. Have you met this question in a real interview? Yes Example Given s = "Hello World", return 5. Note A word is defined as a character sequence consists of non-space characters only. ~~~ ### 題解 關鍵點在于確定最后一個字符串之前的空格，此外還需要考慮末尾空格這一特殊情況，故首先除掉右邊的空白字符比較好。 ### Java ~~~ public class Solution { /** * @param s A string * @return the length of last word */ public int lengthOfLastWord(String s) { if (s == null | s.isEmpty()) return 0; // trim right space int begin = 0, end = s.length(); while (end > 0 && s.charAt(end - 1) == ' ') { end--; } // find the last space for (int i = 0; i < end; i++) { if (s.charAt(i) == ' ') { begin = i + 1; } } return end - begin; } } ~~~ ### 源碼分析 兩根指針。 ### 復雜度分析 遍歷一次，時間復雜度 O(n)O(n)O(n).