// 93. Restore IP Addresses #include "leetcode.h" /* * a valid ip address consists of exactly 4 integers separated by single dots * each integer is between 0 and 255 (inclusive) and cannot have leading 0's * given: string 's' containing only digits, return all possible valid ip * addresses that can be formed by insert dots into 's'. digits cannot be * reordered or removed. return addresses in any order. */ class Solution { public: vector restoreIpAddresses(string s) { vector ans; string ip; dfs(s, 0, 0, ip, ans); return ans; } private: void dfs(string s, int start, int step, string ip, vector &res) { if (start == s.size() && step == 4) { ip.erase(ip.end() - 1); res.push_back(ip); return; } if (s.size() - start > (4 - step) * 3) return; if (s.size() - start < (4 - step)) return; int num = 0; for (int i = start; i < start + 3; i++) { num = num * 10 + (s[i] - '0'); if (num <= 255) { ip += s[i]; dfs(s, i + 1, step + 1, ip + '.', res); } if (num == 0) break; } } }; int main() { Solution obj; for (auto i : obj.restoreIpAddresses("25525511135")) cout << i; // expect: 255.255.11.135","255.255.111.35 cout << endl; for (auto i : obj.restoreIpAddresses("0000")) cout << i; // expect: 0.0.0.0 cout << endl; for (auto i : obj.restoreIpAddresses("101023")) cout << i; // expect: 1.0.10.23,1.0.102.3,10.1.0.23,10.10.2.3,101.0.2.3 cout << endl; }