[LeetCode]Length of Last Word

题目描述

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

.
一个字符串由大小写字母和空格组成，给出其最后一个单词的长度，如果没有，返回0.

解题思路

解决本题的关键就是从尾至头扫描字符串，略去空格，计算出最后一个单词的长度。

代码

public int lengthOfLastWord(String s) {
if(s==null || s.length()==0){
return 0;
}

int posTail = s.length()-1;
int posHead = 0;

while(posTail >=0 && s.charAt(posTail)==' '){
//循环略去空格
posTail--;
}

if(posTail==-1){
return 0;
} else {
posHead = posTail;
while(posHead >= 0 && s.charAt(posHead)!=' '){
posHead--;
}
return posTail - posHead;
}
}