package LeetCode;

import java.util.ArrayList;
import java.util.List;

//2024-01-06-16:00
public class LC_93 {

    static List<String> res = new ArrayList<>();

    public static void main(String[] args) {
        restoreIpAddresses("2736786374048");
    }

    public static List<String> restoreIpAddresses(String s) {
        StringBuilder path = new StringBuilder(s);
        backtracking(path, 0, 0);
        System.out.println(res);
        return res;
    }

    public static void backtracking(StringBuilder s, int startIdx, int pointNums) {
        if (pointNums == 3) {
            if (isValid(s, startIdx, s.length() - 1)) {
                res.add(s.toString());
            }
            return;
        }
        for (int i = startIdx; i < s.length(); i++) {
            if (isValid(s, startIdx, i)) {
                s.insert(i + 1, ".");
                backtracking(s, i + 2, pointNums + 1);
                s.deleteCharAt(i + 1);
            } else break;
        }
    }

    public static boolean isValid(StringBuilder s, int start, int end) {
        if (start > end) return false;
        if (s.charAt(start) == '0' && start != end) return false;
        int num = 0;
        for (int i = start; i <= end; i++) {
            int digit = s.charAt(i) - '0';
            num = num * 10 + digit;
            if (num > 255) return false;
        }
        System.out.println("num:" + s.substring(start, end + 1));
        return true;
    }
}