leetcode restore ip address Java实现

原题目链接：

https://leetcode.com/problems/restore-ip-addresses/description/

java代码：

class Solution {
    public List restoreIpAddresses(String s) {
        ArrayList ips=new ArrayList();
        String current_ip="";
        getAllIP(s,0,0,current_ip,ips);
        return ips;
    }
    
    public void getAllIP(String s,int index,int step,String current_ip,ArrayList ips)
    {
        if(s.length()-index>(4-step)*3)
        {
            return;
        }
        else if(s.length()-index<4-step)
        {
            return;
        }
        else if(step==4&&index==s.length())
        {
            ips.add(current_ip.substring(0,current_ip.length()-1));
        }
        else
        {
            int num=0;
            for(int i=index;i