面试题58：翻转单词顺序
题目要求：
输入一个英文句子，翻转单词顺序，单词内字符不翻转，标点符号和普通字母一样处理。例如输入输入“I am a student.”，则输出“student. a am I”。
解题思路：
首先字符串整体翻转，得到“.tneduts a ma I”；然后以空格作为分隔符进行切分，对于切分下来的每一部分再进行翻转，得到“student. a am I”。
package chapter6;
/**
* Created with IntelliJ IDEA
* Author: ryder
* Date : 2017/8/17
* Time : 16:01
* Description:翻转字符串
**/
public class P284_ReverseWordsInSentence {
public static String reverse(String str){
StringBuilder stringBuilder = new StringBuilder(str);
reverseSubString(stringBuilder,0,stringBuilder.length()-1);
int start = 0,end = stringBuilder.indexOf(" ");
while (start<stringBuilder.length()&&end!=-1){
reverseSubString(stringBuilder,start,end-1);
start = end+1;
end = stringBuilder.indexOf(" ",start);
}
if(start<stringBuilder.length())
reverseSubString(stringBuilder,start,stringBuilder.length()-1);
return stringBuilder.toString();
}
//翻转stringBuilder[start,end]
public static void reverseSubString(StringBuilder stringBuilder,int start,int end){
for(int i=start;i<=start+(end-start)/2;i++){
char temp = stringBuilder.charAt(i);
stringBuilder.setCharAt(i,stringBuilder.charAt(end-i+start));
stringBuilder.setCharAt(end-i+start,temp);
}
}
public static void main(String[] args){
System.out.println(reverse("I am a student."));
}
}
运行结果
student. a am I
