Reverse Words in a String

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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.

思路：1 空值检验，去掉两端的空格

2 以若干个（1个以上）空格为分隔符，将字符串转化为数组；

3 遍历数组的一半，交换i与len-i-1

4.StringBuffer将数组连接起来，记得加上空格

 public String reverseWords(String s) {                if(s==null||"".equals(s.trim())) return s==null?s:s.trim();        s=s.trim();        String[] str=s.split("[\\s]+");        int len=str.length;                for(int i=0;i<len/2;i++){            String s1=str[i];            str[i]=str[len-i-1];            str[len-i-1]=s1;        }        // char[] c=s.toCharArray();        // int len=c.length;                // for(int i=0;i<len/2;i++){                    //     char c1=c[i];        //     c[i]=c[len-i-1];        //     c[len-i-1]=c1;        // }        StringBuffer sb=new StringBuffer();        for(int i=0;i<str.length;i++)        sb.append(str[i]+" ");                return sb.toString().trim();    }

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