resotreIpAddress

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)

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 1 #include <string>
 2 #include <vector>
 3 using namespace std;
 4 class Solution {
 5 public:
 6     vector<string> restoreIpAddresses(string s) {
 7         vector<string> result;
 8         vector<int> path;
 9         dfs(s,0,0,path,result);
10         return result;
11     }
12 private:
13     void dfs(string& s,int start,int num,
14         vector<int>& path,vector<string>& result){
15         if(num == 3) {
16             string str = s;
17             for(int i=0;i<3;i++){
18                 str.insert(path[i]+i,1,‘.‘);
19             }
20             result.push_back(str);
21             return;
22         }
23
24         for(int i=1;i<4;i++){
25             if((start+i)<s.length() && 3-num<=s.substr(start+i).length() && s.substr(start+i).length()<=(3-num)*3){
26                 if(stoi(s.substr(start,i))<=255){
27                     if(i>1 && s[start] ==‘0‘) break;
28                     if(num==2 && stoi(s.substr(start+i))>255) continue;
29                     if(num==2 && s.substr(start+i).length()>1 && s[start+i]==‘0‘) continue;
30
31                     if(path.empty()) path.push_back(i);
32                     else path.push_back(path.back()+i);
33                      dfs(s,start+i,num+1,path,result);
34                      path.pop_back();
35                 }
36             }
37         }
38     }
39 };
40 int main(){
41     string IPaddress="1203045";
42     Solution s;
43     vector<string> result;
44     result = s.restoreIpAddresses(IPaddress);
45     return 0;
46 }