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: DFS.

 1 class Solution {
 2 public:
 3     vector<string> restoreIpAddresses(string s) {
 4         vector<string> res;
 5         string ip;
 6         restoreIpAddressRe(s, res, ip, 0, 0);
 7         return res;
 8     }
 9     
10     void restoreIpAddressRe(string &s, vector<string> &res, string &ip, int deep, int start)
11     {
12         if (deep == 4 && start == s.size())
13             res.push_back(ip);
14         if (deep == 4) return;
15         
16         int num = 0, origSize = ip.size();
17         if (origSize != 0) ip.push_back('.');
18         for (int i = start; i < s.size(); ++i)
19         {
20             num = num * 10 + s[i] - '0';
21             if (num > 255) break;
22             ip.push_back(s[i]);
23             restoreIpAddressRe(s, res, ip, deep + 1, i + 1);
24             if (num == 0) break;
25         }
26         ip.resize(origSize);
27     }
28 };

 

posted @ 2014-04-24 03:29  beehard  阅读(137)  评论(0)  编辑  收藏  举报