Length of Last Word
最后更新于：2022-04-02 01:07:58
# 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.
~~~
### 题解
关键点在于确定最后一个字符串之前的空格，此外还需要考虑末尾空格这一特殊情况，故首先除掉右边的空白字符比较好。
### 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;
}
}
~~~
### 源码分析
两根指针。
### 复杂度分析
遍历一次，时间复杂度 O(n)O(n)O(n).
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