题解 | #识别有效的IP地址和掩码并进行分类统计#

import java.util.*;
public class Main {
        public static void main(String[] args) {
            Scanner sc = new Scanner(System.in);
            int aNum = 0;
            int bNum = 0;
            int cNum = 0;
            int dNum = 0;
            int eNum = 0;
            int errNum = 0;
            int pNum = 0;
            while (sc.hasNextLine()) {
                String str = sc.nextLine();
                String[] strArr = str.split("~");
                int ipFirst = getIpSeg(strArr[0], 0);
                if (ipFirst == 0 || ipFirst == 127) {
                    continue;
                }
                if (maskIsInvaild(strArr[1])) {
                    errNum++;
                    continue;
                }
                if (ipIsInvaild(strArr[0])) {
                    errNum++;
                    continue;
                }
                if (ipFirst >= 1 && ipFirst <= 126) {
                    aNum++;
                }
                if (ipFirst >= 128 && ipFirst <= 191) {
                    bNum++;
                }
                if (ipFirst >= 192 && ipFirst <= 223) {
                    cNum++;
                }
                if (ipFirst >= 224 && ipFirst <= 239) {
                    dNum++;
                }
                if (ipFirst >= 240 && ipFirst <= 255) {
                    eNum++;
                }
                int ipSecond = getIpSeg(strArr[0], 1);
                if (ipFirst == 10 || (ipFirst == 172 && ipSecond >= 16 && ipSecond <=31) || (ipFirst == 192 && ipSecond == 168)) {
                    pNum++;
                }
            }
            System.out.println(aNum + " " + bNum + " " + cNum + " " + dNum + " " + eNum + " " + errNum + " " + pNum);
        }
    
    public static boolean maskIsInvaild(String mask) {
        String[] maskArr = mask.split("\\.");
        if (maskArr.length != 4) {
            return true;
        }
        String maskBinary = toBinary(maskArr[0]) + toBinary(maskArr[1]) + toBinary(maskArr[2]) + toBinary(maskArr[3]);
        if (!maskBinary.matches("[1]{1,}[0]{1,}")) {
            return true;
        }
        return false;
    }
    
    public static String toBinary(String num) {
        String numBinary = Integer.toBinaryString(Integer.valueOf(num));
        while (numBinary.length() < 8) {
            numBinary = "0" + numBinary;
        }
        return numBinary;
    }
    
    public static boolean ipIsInvaild(String ip) {
        String[] ipArr = ip.split("\\.");
        if (ipArr.length != 4) {
            return true;
        }
        if (Integer.valueOf(ipArr[0]) > 255 || Integer.valueOf(ipArr[1]) > 255 || Integer.valueOf(ipArr[2]) > 255 || Integer.valueOf(ipArr[3]) > 255) {
            return true;
        }
        return false;
    }
    
    public static int getIpSeg(String ip, int index) {
        String[] ipArr = ip.split("\\.");
        return Integer.valueOf(ipArr[index]);
    }
}