Restore IP Addresses

Restore IP Addresses

Problem:

Given a string containing only digits, restore it is returning all possible valid IP address combinations.

Ideas:

DFS + backtracking templates

My Code 1:

IsValid to catch to 00 0 010 is illegal data

 Public classSolution { PublicList<string>restoreipaddresses (String s) {if(s = =NULL|| S.length () < 4 | | S.length () > 12)returnlist; Helper (S,0, ""); returnlist; }    Privatelist<string> list =NewArraylist<string>();  Public voidHelper (String s,intcount, String Res) {        if(Count = = 4 && s.equals ("") {list.add (res.substring (1)); return; }         for(inti = 1; I <= s.length () && i <= 3; i++) {String IP= s.substring (0, i); if(Validip (IP)) {helper (s.substring (i), Count+ 1, res + "." +IP); }        }    }     Public Booleanvalidip (String IP) {if(Ip.length () > 1 && ip.charat (0) = = ' 0 ')return false; intValue =integer.parseint (IP); if(Value >= 0 && value <= 255)return true; return false; }}

View Code

The code in code 1 that satisfies the requirements should include the IF (count = = 4 &&!s.equals ("")) return; Early stacks, lest waste of time

My Code 2:

 Public classSolution { PublicList<string>restoreipaddresses (String s) {if(s = =NULL|| S.length () < 4 | | S.length () > 12)returnlist; Helper (S,0, ""); returnlist; }    Privatelist<string> list =NewArraylist<string>();  Public voidHelper (String s,intcount, String Res) {        if(Count = = 4)        {            if(!s.equals (""))return; List.add (Res.substring (1)); return; }         for(inti = 1; I <= s.length () && i <= 3; i++) {String IP= s.substring (0, i); if(Validip (IP)) {helper (s.substring (i), Count+ 1, res + "." +IP); }        }    }     Public Booleanvalidip (String IP) {if(Ip.length () > 1 && ip.charat (0) = = ' 0 ')return false; intValue =integer.parseint (IP); if(Value >= 0 && value <= 255)return true; return false; }}

View Code

Code 2 IsValid code is too ugly, not concise, the following two lines can be merged

My Code 3

 Public classSolution { PublicList<string>restoreipaddresses (String s) {if(s = =NULL|| S.length () < 4 | | S.length () > 12)returnlist; Helper (S,0, ""); returnlist; }    Privatelist<string> list =NewArraylist<string>();  Public voidHelper (String s,intcount, String Res) {        if(Count = = 4)        {            if(!s.equals (""))return; List.add (Res.substring (1)); return; }         for(inti = 1; I <= s.length () && i <= 3; i++) {String IP= s.substring (0, i); if(Validip (IP)) {helper (s.substring (i), Count+ 1, res + "." +IP); }        }    }     Public Booleanvalidip (String IP) {if(Ip.length () > 1 && ip.charat (0) = = ' 0 ')return false; intValue =integer.parseint (IP); returnValue >= 0 && value <= 255; }}

View Code

Restore IP Addresses