LeetCode : Restore IP Address_Jane

Question :

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)

思路：

設函數IPV4（4）=（1+2+3）*IPV4（3），既第一字段取一個數字，後面取三個Ip地址段，或者第一字段取二個數字，後面取三個Ip地址段，或者第一字段取三個數字，後面取三個Ip地址段，爲迭代程序。

package String.Cheng;

import java.util.ArrayList;

public class FindAllIpAddress {
	public static boolean IsPartAddress(String s) {
		boolean state = true;
		if (s.substring(0) == "0" || Integer.parseInt(s) > 255) {
			state = false;
		}
		return state;
	}

	public static ArrayList<String> FindIpAddress(String s, int time) {
		ArrayList<String> PartArrayList = new ArrayList<String>();
		ArrayList<String> isList = new ArrayList<String>();
		if (time == 1 && IsPartAddress(s)) {
			isList.add(s);
			return isList;
		}
		if (s.length() > 1 && s.length() <= time * 3 && s.length() >= time
				&& IsPartAddress(s.substring(0, 1))) {
			PartArrayList = FindIpAddress(s.substring(1), time - 1);
			if (PartArrayList != null && PartArrayList.size() > 0) {
				for (int i = 0; i < PartArrayList.size(); i++) {
					isList.add(s.substring(0, 1) + "." + PartArrayList.get(i));
				}
			}
		}

		if (s.length() > 2 && s.length() <= time * 3 && s.length() >= time
				&& IsPartAddress(s.substring(0, 2))) {
			PartArrayList = FindIpAddress(s.substring(2), time - 1);
			if (PartArrayList != null && PartArrayList.size() > 0) {
				for (int i = 0; i < PartArrayList.size(); i++) {
					isList.add(s.substring(0, 2) + "." + PartArrayList.get(i));
				}
			}
		}

		if (s.length() > 3 && s.length() <= time * 3 && s.length() >= time
				&& IsPartAddress(s.substring(0, 3))) {
			PartArrayList = FindIpAddress(s.substring(3), time - 1);
			if (PartArrayList != null && PartArrayList.size() > 0) {
				for (int i = 0; i < PartArrayList.size(); i++) {
					isList.add(s.substring(0, 3) + "." + PartArrayList.get(i));
				}
			}
		}
		return isList;

	}

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		System.out.println(FindIpAddress("25525511135", 4));

	}

}