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".

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.

题目大意：给一个String，以空格分隔，以单词为单位反转这个String。

解题思路：用java自带的split，拆成数组，然后组合。。。

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