LeetCode:Restore IP Address

 1 class Solution {
 2 public:
 3 
 4     bool dfs(string input, int number, string ipAddress, vector<string> &result){
 5         if(input.length() == 0){
 6             return false;
 7         }
 8         if(number == 3){
 9             int addressNumber = stoi(input);
10             if(input[0] == ‘0‘){
11                 if(!(input.length() == 1 && addressNumber == 0))
12                     return false;
13             }
14             if(addressNumber <= 255){
15                 ipAddress = ipAddress + input;
16                 result.push_back(ipAddress);
17                 return true;
18             }else{
19                 return false;
20             }
21         }else{
22             if(input.length() >= 1){
23                 dfs(input.substr(1), number + 1, ipAddress + input.substr(0, 1) + ".", result);
24             }
25             if(input.length() >= 2 && input[0] != ‘0‘){
26                 dfs(input.substr(2), number + 1, ipAddress + input.substr(0, 2) + ".", result);
27             }
28             if(input.length() >= 3 && input[0] != ‘0‘){
29                 int addressNumber = stoi(input.substr(0, 3));
30                 if(addressNumber <= 255){
31                     dfs(input.substr(3), number + 1, ipAddress + input.substr(0, 3) + ".", result);
32                 }
33             }
34         }
35         return true;
36     }
37 
38     vector<string> restoreIpAddresses(string s) {
39         vector<string> result;
40         if(s.length() == 0 || s.length() > 12){
41             return result;
42         }
43         string temp = "";
44         dfs(s, 0, temp, result);
45         return result;
46     }
47 };