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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#include <string>
#include <vector>
using namespace std;
class Solution {
public:
vector<string> restoreIpAddresses(string s) {
vector<string> result;
vector<int> path;
dfs(s,0,0,path,result);
return result;
}
private:
void dfs(string& s,int start,int num,
vector<int>& path,vector<string>& result){
if(num == 3) {
string str = s;
for(int i=0;i<3;i++){
str.insert(path[i]+i,1,'.');
}
result.push_back(str);
return;
}

for(int i=1;i<4;i++){
if((start+i)<s.length() && 3-num<=s.substr(start+i).length() && s.substr(start+i).length()<=(3-num)*3){
if(stoi(s.substr(start,i))<=255){
if(i>1 && s[start] =='0') break;
if(num==2 && stoi(s.substr(start+i))>255) continue;
if(num==2 && s.substr(start+i).length()>1 && s[start+i]=='0') continue;

if(path.empty()) path.push_back(i);
else path.push_back(path.back()+i);
dfs(s,start+i,num+1,path,result);
path.pop_back();
}
}
}
}
};
int main(){
string IPaddress="1203045";
Solution s;
vector<string> result;
result = s.restoreIpAddresses(IPaddress);
return 0;
}