【LeetCode】Reverse Words in a String

题目：

Given an input string, reverse the string word by word.

For example,

Given s = "

the
sky is blue

",

return "

blue is sky the

".

解答：

首先理解题意很重要，不然会浪费很多时间在细节上，先理清题目隐藏的一些细节：1，字符串的两端的空格要去掉；2，单词间只保留一个空格，如以下测试用例：

"            "
"a        "
"             a        "
"             a"
"             a                     b        "
"             a b       "
"             a  b"
"a  b      "
"             a  b                c d e f                          g      "

代码如下：

class Q151_ReverseWords{

//ac
public static String reverseWords(String s){
if(s=="") return "";
String str="";
int start=0,end;
for(int i=s.length()-1;i>=0;){
while(i>=0&&s.charAt(i)==' ')
i--;
if(i!=start) str+=" ";
end=i;
while(i>=0&&s.charAt(i)!=' ') i--;
start=i;
str+=s.substring(start+1,end+1);
}
//去除两端空格
start=0;
end=str.length()-1;
while(start<=end&&str.charAt(start)==' ')
start++;
while(start<=end&&str.charAt(end)==' ')
end--;
return str.substring(start,end+1);
}
public static void main(String[] args){
String str="   a   b    ";
System.out.print(str);
System.out.println("--");
System.out.print(reverseWords(str));
System.out.println("--");
}
}

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