LeetCode | Reverse Words in a String

題目

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.

• 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. 分析

  正統的做法就是自己去逐個找到每個單詞，從前往後還是從後往前其實都差不多，都要翻轉：要麼是翻轉字母（從後往前）、要麼翻轉單詞（從前往後）。

  這裡給出的是用java自帶的split方法，幫助我們以“ ”進行切割，代碼看上去會比較簡潔明了。

  代碼

  public class ReverseWordsInAString {
  	public String reverseWords(String s) {
  		if (s == null || s.length() == 0) {
  			return "";
  		}
  
  		String[] array = s.split(" ");
  		StringBuilder sb = new StringBuilder();
  		for (int i = array.length - 1; i >= 0; --i) {
  			if (!array[i].equals("")) {
  				sb.append(array[i]).append(" ");
  			}
  		}
  		return sb.length() == 0 ? "" : sb.substring(0, sb.length() - 1);
  	}
  }