Given a string containing only digits, restore it by returning all possible valid IP address combinations.
Example:
Input: "25525511135" Output: ["255.255.11.135", "255.255.111.35"]class Solution { public List<String> restoreIpAddresses(String s) { List<String> res = new ArrayList<>(); addResult(res, s, 0, 1, ""); return res; } void addResult(List<String> res,String s,int begin,int segment,String tmp) { if(segment >5) { return; } if(begin == s.length() && segment==5) { res.add(tmp.substring(0,tmp.length()-1).toString()); return; } //当前段为长度i for(int i=1;i<=3;i++) { if(begin+i > s.length()) { return ; } if(s.charAt(begin)=='0' && i>1) { return ; } if(Integer.valueOf(s.substring(begin, begin+i)) > 255) { return ; } String tmpV = s.substring(begin, begin+i)+"."; tmp+=tmpV; addResult(res,s,begin+i,segment+1,tmp); tmp=tmp.substring(0, tmp.length()-tmpV.length()); } } }
把每段进行遍历，符合一定条件
