93.复原IP地址
本期本来是很有难度的,不过 大家做完 分割回文串 之后,本题就容易很多了
题目链接/文章讲解:代码随想录
视频讲解:回溯算法如何分割字符串并判断是合法IP?| LeetCode:93.复原IP地址_哔哩哔哩_bilibili
class Solution {private List<String> result = new ArrayList<>();public List<String> restoreIpAddresses(String s) {if(s.length() > 12 || s.length() < 4){return result;}restoreIp(new StringBuilder(s), 0, 3);return result; }public void restoreIp(StringBuilder sb , int starindex , int pointnum){if(pointnum == 0){if(isValid(sb, starindex, sb.length() - 1)){result.add(sb.toString());return;}}for(int i = starindex; i < sb.length() ; i++){if(isValid(sb, starindex, i)){sb.insert(i+1, '.');restoreIp(sb, i + 2, pointnum - 1);sb.deleteCharAt(i+1);}else{break;