DSA/C++/LeetCode/0093.cpp at main · spycedcoffee/DSA · GitHub

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class Solution {
public:
    void dfs(string& s, int start, int step, string ip, vector<string>& result) {
        int siz = s.size();

        if(start == siz && step == 4) {
            ip.erase(ip.end() - 1);
            result.push_back(ip);
            return;
        }

        if(siz - start > (4 - step) * 3)
            return;

        if(siz - 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 + '.', result);
            }

            if(num == 0)
                break;
        }
    }

    vector<string> restoreIpAddresses(string s) {
        vector<string> result;
        string ip;

        dfs(s, 0, 0, ip, result);

        return result;
    }
};