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)
最简单的情况,遍历……
class Solution {
public:
vector<string> restoreIpAddresses(string s) {
// Start typing your C/C++ solution below
// DO NOT write int main() function
vector<string> ret;
if(s.size()>12)
return ret;
int length=s.size();
for(int i=1 ; i<4 ; i++)
for(int j=1 ; j<4 ; j++)
for(int k=1 ; k<4 ; k++)
for(int l=1 ; l<4 ; l++){
if(i+j+k+l!=length)
continue;
string s1,s2,s3,s4;
s1.append(s.begin(),s.begin()+i);
s2.append(s.begin()+i,s.begin()+i+j);
s3.append(s.begin()+i+j,s.begin()+i+j+k);
s4.append(s.begin()+i+k+j,s.end());
if(check(s1)&&check(s2)&&check(s3)&&check(s4)){
string s=s1+"."+s2+"."+s3+"."+s4;
ret.push_back(s);
}
}
return ret;
}
bool check(const string& s){
if(s=="")
return false;
int n=s.size();
if(n>1 && s[0]=='0')
return false;
int num=0;
for(int i=0 ; i<n ; i++){
num=num*10+(s[i]-'0');
}
if(num>255)
return false;
return true;
}
};