翻转单词顺序列
- 算法：首先将整个句子翻转一遍，然后对每个单词进行翻转
- 需要考虑两种边界情况
- 输入字符串是空字符串
- 输入的字符串只有一个单词，不需要进行翻转（这种情况更难处理）：使用一个专门检查字符串是否为单个单词的函数即可
- 残留问题：本地能够通过对于输入字符串为”“和” “的输出，OJ上会出现对输入” “的异常java.lang.StringIndexOutOfBoundsException: String index out of range: 3
分析
public class Solution {
public static String ReverseSentence(String str) {
if(str.equals(" "))
return str;
if(str == null || str == "") //如果是空字符串
return str;
int len = str.length();
char[] chars = str.toCharArray();
if(checkIfOneWord(chars))
return str;
ReverseWord(chars,0,len-1);
int i = 0;
int before_blank = 0;
int next_blank = 0;
while(i < len){
if(chars[i] == ' '){
next_blank = i;
ReverseWord(chars,before_blank,next_blank-1);
i++;
before_blank = i;
} else{
i++;
}
}
String result = new String(chars);
return result;
}
public static void ReverseWord(char[] chars, int left, int right){
while(left < right){
char tmp = chars[left];
chars[left] = chars[right];
chars[right] = tmp;
left++;
right--;
}
}
public static boolean checkIfOneWord(char[] chars){
for(int i=0; i < chars.length; i++){
if(chars[i] == ' ')
return false;
}
return true;
}
public static void main(String[] args){
String str = "I am a student.";
String s2 ="Wonderful";
System.out.println(ReverseSentence(" "));
System.out.println(ReverseSentence(str));
System.out.println(ReverseSentence(s2));
}
}