Reverse Words in a String

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本文探讨了如何在编程中反转整个字符串，并特别关注如何处理和反转字符串中的单词，包括处理空格、前后导空格及多个连续空格的情况。

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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`".

Update (2015-02-12):
For C programmers: Try to solve it in-place in O(1) space.

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.

Java代码：

public class Solution {
    public String reverseWords(String s) {
        String s1 = s.trim();
		if (s1.length() == 0)
			return s1;

		String[] word = s.split("\\s+");
		int len = word.length;
		StringBuilder sb = new StringBuilder();
		if (word[0].equals("") || word[len - 1].equals("")) {
			if (word[0].equals("") && word[len - 1].equals("")) {
				for (int i = len - 2; i > 1; i--) {
					sb.append(word[i]);
					sb.append(" ");
				}
				sb.append(word[1]);
			} else if (word[0].equals("")) {
				for (int i = len - 1; i > 1; i--) {
					sb.append(word[i]);
					sb.append(" ");
				}
				sb.append(word[1]);
			} else {
				for (int i = len - 2; i > 0; i--) {
					sb.append(word[i]);
					sb.append(" ");
				}
				sb.append(word[0]);
			}
		} else {
			for (int i = len - 1; i > 0; i--) {
				sb.append(word[i]);
				sb.append(" ");
			}
			sb.append(word[0]);
		}

		return sb.toString();
    }
}