public static void main(String[] args) {

Solution93 s = new Solution93();

String[] cases = {"25525511135"};

for (String c : cases) System.out.println(s.restoreIpAddresses(c));

}

public List<String> restoreIpAddresses(String s) {

List<String> result = new LinkedList<>();

char dot = '.';

int len = s.length(), max = Math.min(len - 2, 6);

for (int mid = Math.max(2, len - 6); mid <= max; mid++) {

List<Integer> p = new LinkedList<>(), n = new LinkedList<>();

int temp = Math.min(mid - 1, 3);

for (int i = Math.max(1, mid - 3); i <= temp; i++)

if (isByte(s, 0, i) && isByte(s, i, mid))

p.add(i);

if (p.isEmpty()) continue;

temp = Math.min(len - 1, mid + 3);

for (int i = Math.max(mid + 1, len - 3); i <= temp; i++)

if (isByte(s, mid, i) && isByte(s, i, len))

n.add(i);

if (n.isEmpty()) continue;

for (int a : p)

for (int b : n)

result.add(new StringBuilder(s).insert(b, dot).insert(mid, dot).insert(a, dot).toString());

}

return result;

}

private static boolean isByte(String s, int x, int y) {

switch (y - x) {

case 1:

return true;

case 2:

return s.charAt(x) != '0';

case 3:

break;

default:

return false;

}

switch (s.charAt(x)) {

case '1':

return true;

case '2':

break;

default:

return false;

}

char c = s.charAt(x + 1);

if (c < '5') return true;

if (c > '5') return false;

return s.charAt(x + 2) <= '5';

}