package learn.fresh;

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

//

//For example,

//Given s = " the sky is blue ",

//return " blue is sky the ".

//

//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.

public class ReverseWordsinaString {

// 正统的做法就是自己去逐个找到每个单词，从前往后还是从后往前其实都差不多，

// 都要翻转：要么是翻转字母（从后往前）、要么翻转单词（从前往后）。

//

// 这里给出的是用java自带的split方法，帮助我们以“ ”进行切割，代码看上去会比较简洁明了。

public String reverseWords(String s) {

if (s == null || s.length() == 0) {

return "";

}

String[] array = s.split(" +"); //表示1~n个空格 split 2个 5个都split一次

StringBuilder sb = new StringBuilder();

for (int i = array.length - 1; i >= 0; i--) { //从数组最后一个词往前遍历

sb.append(array[i]).append(" "); //放一个词后加一个空

}

return sb.length() == 0 ? "" : sb.toString().trim();

}

}