【LeetCode】Reverse Words in a String

Given an input string, reverse the string word by word.

For example,

Given s = "

the sky is blue

",

return "

blue is sky the

".

click to show clarification.

Clarification:

What constitutes a word?

A sequence of non-space characters constitutes a word.
Could the input string contain leading or trailing spaces?

Yes. However, your reversed string should not contain leading or trailing spaces.
How about multiple spaces between two words?

Reduce them to a single space in the reversed string.
1.利用split(" ")函数进行切分
2.首先要过滤掉首尾的空格；
3.注意两个单词之间的多个空格只要保留一个

public class Solution {
public  String reverseWords(String s) {

String[] tmp = s.split(" ");
String ans = null;
int len = tmp.length;

if(len == 0) return "";
else
{
int i = 0;
while(i<len)
{
if(tmp[i].equals("")) i++;
else break;
}
int begin = i;
if(begin == len)  return "";
int j = len - 1;
while(j>=0)
{
if(tmp[j].equals("")) j--;
else break;
}
int end = j;
int flag = 0;
ans = tmp[end];

for(int k = end - 1;k >= begin;k--)
{
if(tmp[k].equals("")) flag = 1;
else flag = 0;
if(flag == 0)
{
ans = ans + " " +tmp[k];
}

}
}
return ans;
}
}