Q2:Reverse Words in a String

Clarification:

• What constitutes a word?
  A sequence of non-space characters constitutes a word.
• Could the input string contain leading or trailing spaces?
  Yes. However, your reversed string should not contain leading or trailing spaces.
• How about multiple spaces between two words?
  Reduce them to a single space in the reversed string.

MyAnswer 1 (Java):

 public class Solution {
     public String reverseWords(String s) {
         String result = "";
         int i = 0;
         int j = s.length();
         for(i = s.length()-1; i >= 0; i--)
         {
             if(s.charAt(i) == ' ')
             {
                 if(i == s.length()-1)
                 {
                     j = i;
                     //continue;
                 }
                 else if(i == 0)
                 {
                     //i++;
                     break;
                 }
                 else if(j == i+1)
                 {
                     j = i;
                     //continue;
                 }
                 else
                 {
                     result = result.concat(s.substring(i+1,j)+" ");
                     j = i;
                 }
             }
         }
         result = result.concat(s.substring(i+1,j));
         if(!result.isEmpty() && result.charAt(result.length()-1) == ' ')
             result = result.substring(0,result.length()-1);
         return result;
     }
 }

使代码更加精简，改为：

MyAnswer 2(Java):

 public class Solution {
     public String reverseWords(String s) {

         String result = "";
         int j = s.length();
         int i = j-1;

         for(; i >= 0; i--)
         {
             if(s.charAt(i) == ' ')
             {
                 if(i == 0)
                 {
                     break;
                 }
                 else if(i != s.length()-1 && j != i+1)
                 {
                     result = result.concat(s.substring(i+1,j)+" ");
                 }
                 j = i;
             }
         }

         result = result.concat(s.substring(i+1,j));

         int k = result.length();
         if(!result.isEmpty() && result.charAt(k-1) == ' ')
             result = result.substring(0,k-1);
         return result;
     }
 }

MyAnswer3 (C++):

 class Solution {
 public:
     void reverseWords(string &s) {
         string result = "";
         int j = ;
         int i;
         for(i = s.length()-; i >= ; i--)
         {
             if(s[i] == ' ')
             {
                 if(j == )
                     continue;
                 result = result + s.substr(i+, j) + " ";
                 j = ;
                 continue;
             }
             j++;
         }
         result = result + s.substr(i+, j);
         s = (result[result.length()-] == ' ')?result.substr(,result.length()-):result;
     }
 };