【LeetCode刷题Java版】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.

package com.liuhao.acm.leetcode;

/**
 * @author liuhao
 * 
 *         Given an input string, reverse the string word by word. For example,
 *         Given s = "the sky is blue", return "blue is sky the".
 */
public class ReverseWords {

	public static String reverseWords(String s) {

		// 若输入字符串直接是空串，则直接返回该字符串
		if (s.equals("")) {
			return "";
		}

		// 将字符串按空格"\\s{1,}"进行分割，一个或者多个空格的正则："\\s{1,}"
		String[] strArr = s.split("\\s{1,}");
		int len = strArr.length;

		// 分割后字符串变成空串，直接返回
		if (len == 0) {
			return "";
		}

		// 用StringBuilder更加有效
		StringBuilder sb = new StringBuilder("");

		// 反向输出之前分割的字符串数组
		for (int i = len - 1; i >= 0; i--) {
			if (!strArr[i].equals("")) {
				sb.append(strArr[i]);
				sb.append(" ");
			}
		}

		sb.deleteCharAt(sb.lastIndexOf(" "));
		
		return sb.toString();
	}

	public static void main(String[] args) {
		System.out.println(reverseWords(""));
	}

}