Today I have done leetcode's January LeetCoding Challenge with cpp.

January LeetCoding Challenge 21

Description

Restore IP Addresses

A valid IP address consists of exactly four integers separated by single dots. Each integer is between 0 and 255 (inclusive) and cannot have leading zeros.

For example, "0.1.2.201" and "192.168.1.1" are valid IP addresses, but "0.011.255.245", "192.168.1.312" and "192.168@1.1" are invalid IP addresses.

Given a string s containing only digits, return all possible valid IP addresses that can be formed by inserting dots into s. You are not allowed to reorder or remove any digits in s. You may return the valid IP addresses in any order.

Example 1:

Input: s = "25525511135"
Output: ["255.255.11.135","255.255.111.35"]

Example 2:

Input: s = "0000"
Output: ["0.0.0.0"]

Example 3:

Input: s = "101023"
Output: ["1.0.10.23","1.0.102.3","10.1.0.23","10.10.2.3","101.0.2.3"]

Constraints:

1 <= s.length <= 20
s consists of digits only.

Solution

class Solution {
  int len;
  int minmax[4][2] = {{}, {-1, 10}, {9, 100}, {99, 256}};
  void addIP(
    vector<string> &answer,
    vector<string> &currentIP
  ) {
    string ip;
    for(auto subnet : currentIP) {
      ip += subnet;
      ip.push_back('.');
    }
    ip.pop_back();
    answer.emplace_back(ip);
  }
  void dfs(
    vector<string> &answer,
    vector<string> &currentIP,
    string &s,
    int pos
  ) {
    if(pos == len) {
      if(currentIP.size() == 4) addIP(answer, currentIP);
      return;
    }
    for(int i = 1; i < 4 && pos + i <= s.length(); ++i) {
      string subnet = s.substr(pos, i);
      int n = stoi(subnet);
      if(n <= minmax[i][0]) break;
      if(n < minmax[i][1]) {
        currentIP.emplace_back(subnet);
        dfs(answer, currentIP, s, pos + i);
        currentIP.pop_back();
      }
    }
  }
public:
  vector<string> restoreIpAddresses(string s) {
    len = s.length();
    vector<string> answer;
    vector<string> ip;
    dfs(answer, ip, s, 0);
    return answer;
  }
};

// Accepted
// 145/145 cases passed (8 ms)
// Your runtime beats 19.08 % of cpp submissions
// Your memory usage beats 70.83 % of cpp submissions (6.6 MB)

2023-01-21 Daily Challenge

January LeetCoding Challenge 21

Description

Solution