Reverse Words in a String

Reverse Words in a String

 

Given an input string, reverse the string word by word.
For example,
Given s = "the sky is blue",
return "blue is sky the".

Naive Way: 如果能使用String.split()就会很方便。

如答案所说，使用String.split() 是需要两次扫描的。如果从后往前扫String，就只需要一次扫面。

 public class Solution {  
   public String reverseWords(String s) {  
     StringBuilder rslt = new StringBuilder();  
     String[] str = s.split(" ");  
     for(int i = str.length-1;i >= 0;i--){  
       if(i!=str.length-1 && str[i].length()!=0) rslt.append(" ");  
       rslt.append(str[i]);  
     }  
     return rslt.toString();  
   }  
 }   

这次从后往前扫，只需要一次。

 public class Solution {  
   public String reverseWords(String s) {  
     StringBuilder rslt = new StringBuilder();  
     int i = s.length(), j = s.length();  
     while(--i >= -1){  
       if(i==-1 || s.charAt(i) == ' '){  
         if(i+1!=j && rslt.length()!=0) rslt.append(" ");  
         rslt.append(s.substring(i+1,j));  
         j = i;  
       }  
     }  
     return rslt.toString();  
   }  
 }