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| public List<String> restoreIpAddresses(String s) {
List<String> result = new ArrayList<>();
if (s == null || s.length() == 0) {
return result;
}
search(s.toCharArray(), 0,0, "", result);
return result;
}
private void search(char[] chars, int index, int fields, String cur, List<String> result) {
if (fields == 4 && index == chars.length) {
result.add(cur.substring(0, cur.length() - 1));
return;
}
if (fields == 4 || index == chars.length) {
return;
}
if (chars[index] == '0') {
search(chars, index + 1, fields + 1, cur + new String(chars, index, 1) + ".", result);
} else {
if (index + 2 < chars.length && Integer.parseInt(new String(chars, index, 3)) <= 255) {
search(chars, index + 3, fields + 1, cur + new String(chars, index, 3) + ".", result);
}
if (index + 1 < chars.length) {
search(chars, index + 2, fields + 1, cur + new String(chars, index, 2) + ".", result);
}
search(chars, index + 1, fields + 1, cur + new String(chars, index, 1) + ".", result);
}
}
|
