LeetCode OJ：Restore IP Addresses（存储IP地址）

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)

典型的dfs，但是要点是注意什么才是真的ip地址，代码如下：

class Solution {
public:
vector<string> restoreIpAddresses(string s) {
if (s.size() > 12) return ret;
dfs(s, 0, 0);
return ret;
}

bool check(string &s)
{
if (s.size() == 1)
return "0" <= s && s <= "9";
else if (s.size() == 2)
return "10" <= s && s <= "99";
else if (s.size() == 3)
return "100" <= s && s <= "255";
else
return false;
}

void dfs(const string & s, int start, int nth)
{
if (nth == 4 && start != s.size())
return;
else if (nth == 4 && start == s.size()){
string tmp = "";
for (int i = 0; i < 3; ++i){
tmp += tmpRes[i];
tmp += ".";
}
tmp += tmpRes[3];    //为了凑格式
ret.push_back(tmp);
}
else
for (int i = 1; i < 4; ++i){
if(start + i <= s.size()){
string tmp = s.substr(start, i);
if(check(tmp)){
tmpRes.push_back(tmp);
dfs(s, start + i, nth + 1);
tmpRes.pop_back();
}
}
}
}

private:
vector<string> tmpRes;
vector<string> ret;
};

写的有点乱了 ，见谅见谅