过滤白名单算法

来源：互联网发布：godaddy 域名赎回期编辑：程序博客网时间：2024/05/02 02:51

昨天面试的时候，面试官出了一道算法题，当时头脑有点乱，没有想出来，现在把它写出来

题目：给定几个白名单网段，例如 "172.16.0.0/17", "192.168.0.0/24", "10.10.10.10/9"，现在有个请求过来，怎么快速确认请求IP是否在白名单中？

package common;import org.junit.Test;public class WhiteListTest{private String[] whiteList = { "172.16.0.0/17", "192.168.0.0/24", "10.10.10.10/9" };@Testpublic void test(){String testIp = "192.168.0.1";for (String net : whiteList){NetworkOffset offset = new NetworkOffset(net);System.out.println(offset);if (offset.matches(testIp)){System.out.println("found");}}}private static class NetworkOffset{private int mask;private int baseIp;NetworkOffset(String net){init(net);}private void init(String net){mask = Integer.valueOf(net.split("/")[1]);mask = 0xFFFFFFFF << (32-mask);String address = net.split("/")[0];baseIp = parseAddr(address);}boolean matches(int ip){return (baseIp & mask) == (ip & mask);}boolean matches(String ip){return matches(parseAddr(ip));}private int parseAddr(String addr){String[] array = addr.split("\\.");int ip = 0;for (int i = 0; i < array.length; i++){int part = (Integer.parseInt(array[i]) & 0xFF) << (24 - 8 * i);ip = ip | part;}return ip;}String first(){int firstIp = baseIp & mask | 0x01;return toIpString(firstIp);}String last(){int lastIp = baseIp & mask | (~mask & 0xFFFFFFFE);return toIpString(lastIp);}private String toIpString(int ip){String part1 = String.valueOf(ip >> 24 & 0xFF);String part2 = String.valueOf(ip >> 16 & 0xFF);String part3 = String.valueOf(ip >> 8 & 0xFF);String part4 = String.valueOf(ip & 0xFF);return part1 + "." + part2 + "." + part3 + "." + part4;}String broadcast(){int broadcastIp = baseIp & mask | (~mask);return toIpString(broadcastIp);}@Overridepublic String toString(){return "NetworkOffset [mask=" + Integer.toBinaryString(mask) + ", baseIp=" + Integer.toBinaryString(baseIp)+ ", firstIp=" + first() + ", lastIp=" + last() + ", broadcastIp=" + broadcast() + "]";}}}

阅读全文

0 0