Reverse Words in a String @LeetCode

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.

	package leetcode;
	import java.util.ArrayList;
	/**
	* Solution: String split and construct.
	*
	* Take care:
	* !"".equals(words[i]) but not " ". after split,there's ""
	*
	* Test Case:
	* " a bb" --> "bb a"
	* " " --> "" this situation, sb.length() == 0
	* @author jeffwan
	* @date Apr 1, 2014
	*/
	public class ReverseWords {
	public String reverseWords(String s) {
	if (s == null || s.length() == 0) {
	return "";
	}
	String[] words = s.split(" "); //Get every single word.
	StringBuilder sb = new StringBuilder();
	for (int i = words.length - 1; i >= 0; i--) {
	if (!"".equals(words[i])) {
	sb.append(words[i] + " ");
	}
	}
	return sb.length() == 0 ? "" : sb.toString().substring(0, sb.length() - 1);
	}
	// My way split word is not clear efficiency enough.
	// I go pass every char to see if it's " ".Should use string.split(" ") direcly.
	public String reverseWords2(String s) {
	if (s == null || s.length() == 0) {
	return "";
	}
	ArrayList<String> list = new ArrayList<String>();
	s = s.trim();
	int wordBegin = 0;
	for (int i = 0; i < s.length(); i++) {
	if (' ' == s.charAt(i)) {
	list.add(0, s.substring(wordBegin, i));
	while (' ' == s.charAt(i)) {
	i++;
	}
	wordBegin = i;
	}
	}
	list.add(0, s.substring(wordBegin, s.length()));
	StringBuilder sb = new StringBuilder();
	for (String word : list) {
	sb.append(word + " ");
	}
	return sb.toString().substring(0, sb.length() - 1);
	}
	}

view raw ReverseWords.java hosted with ❤ by GitHub