Restore IP Addresses

Given a string containing only digits, restore it by returning all possible valid IP address combinations.

For example:
Given "25525511135",

return ["255.255.11.135", "255.255.111.35"]. (Order does not matter)

Solution:

注意这里if(tmp < 256 && tmp.toString().equals(s.substring(pos, pos + j)))

如果不加tmp.toString().equals(s.substring(pos, pos + j)), 则可能会出现001 这种情况, 即高位为0.

 1 public class Solution {
 2     ArrayList<String> result = null;
 3     public ArrayList<String> restoreIpAddresses(String s) {
 4         // IMPORTANT: Please reset any member data you declared, as
 5         // the same Solution instance will be reused for each test case.
 6         result = new ArrayList<String>();
 7         getAddress(s, 0, 4, new StringBuffer());
 8         return result;
 9     }
10     public void getAddress(String s, int pos, int num, StringBuffer sb){
11         if(num == 0 || pos == s.length()){
12             if(pos == s.length() && num == 0){
13                 result.add(sb.substring(0, sb.length() - 1));
14             }
15             return;
16         }
17         for(int j = 1; j < 4 && pos + j <= s.length(); j ++){
18             Integer tmp = Integer.valueOf(s.substring(pos, pos + j));
19             if(tmp < 256 && tmp.toString().equals(s.substring(pos, pos + j))){
20                 sb.append(s.substring(pos, pos + j));
21                 sb.append(".");
22                 getAddress(s, pos + j, num - 1, sb);
23                 sb.delete(sb.length() - j - 1, sb.length());
24             }
25         }
26     }
27 }

 

posted on 2013-11-14 17:44  Step-BY-Step  阅读(200)  评论(0编辑  收藏  举报

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