int main(void)
{
char s[] = "19216811";
int ret = 0;
restoreIpAddresses(s, &ret);
return(0);
}
void restoreIpAddresses(int index,int ipNum,
string& str,string& work,vector<string>& ret){
int size=str.size();
if(ipNum>4)
return ;
if(index==size){
if(ipNum==4){
ret.push_back(work);
ret[ret.size()-1].pop_back();
}
return ;
}
int ipTmp=0;
for(int i=0;i<3;i++){
if(index+i>=size)
break;
ipTmp=ipTmp*10+str[index+i]-'0';
if((size-1-index-i)<=3*(3-ipNum)){
if((i!=0)&&(str[index]=='0'))
break ;
if((i==2)&&(ipTmp>255))
continue;
for(int j=0;j<=i;j++)
work.push_back(str[index+j]);
work.push_back('.');
restoreIpAddresses(index+i+1,ipNum+1,str,work,ret);
for(int j=0;j<=i+1;j++)
work.pop_back();
}
}
}
vector<string> restoreIpAddresses(string s) {
vector<string> ret;
if(s.size()>0){
string work;
restoreIpAddresses(0,0,s,work,ret);
}
return ret;
}