题解 | #识别有效的IP地址和掩码并进行分类统计#

import java.util.Scanner;

// 注意类名必须为 Main, 不要有任何 package xxx 信息
public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        // 注意 hasNext 和 hasNextLine 的区别
        // while (in.hasNextInt()) { // 注意 while 处理多个 case
        //     int a = in.nextInt();
        //     int b = in.nextInt();
        //     System.out.println(a + b);
        // }
        int[] counts = new int[7];
        while (in.hasNextLine()) {
            String line = in.nextLine();
            String[] ip = line.split("~")[0].split("\\.");
            if (ip.length != 4) {
                counts[5]++;
                continue;
            } 
            int ip0 = 0, ip1 = 0, ip2 = 0, ip3 = 0;
            int code0 = 0, code1 = 0, code2 = 0, code3 = 0;
            try {
                ip0 = Integer.parseInt(ip[0]);
                ip1 = Integer.parseInt(ip[1]);
                ip2 = Integer.parseInt(ip[2]);
                ip3 = Integer.parseInt(ip[3]);
                if (ip0 == 0 || ip0 == 127) {
                    continue;
                }
                String[] code = line.split("~")[1].split("\\.");
                code0 = Integer.parseInt(code[0]);
                code1 = Integer.parseInt(code[1]);
                code2 = Integer.parseInt(code[2]);
                code3 = Integer.parseInt(code[3]);
            } catch (NumberFormatException e) {
                counts[5]++;
                continue;
            }

            // 判断子网掩码是否合法
            StringBuilder builder = new StringBuilder();
            String codeBinary = builder.append(toBinary(code0))
                                .append(toBinary(code1))
                                .append(toBinary(code2))
                                .append(toBinary(code3))
                                .toString();
            if (codeBinary.contains("01") || !codeBinary.contains("0") || !codeBinary.contains("1")) {
                counts[5]++;
                continue;
            }

            boolean b = ip1 >= 0 && ip1 <= 255 && ip2 >= 0 && ip2 <= 255 && ip3 >= 0 && ip3 <= 255;

            if (!b) {
                counts[5]++;
                continue;
            }
            if (ip0 >= 1 && ip0 <= 126) {
                counts[0]++;
            } else if (ip0 >= 128 && ip0 <= 191) {
                counts[1]++;
            } else if (ip0 >= 192 && ip0 <= 223) {
                counts[2]++;
            } else if (ip0 >= 224 && ip0 <= 239) {
                counts[3]++;
            } else if (ip0 >= 240 && ip0 <= 255) {
                counts[4]++;
            } else {
                counts[5]++;
                continue;
            }

            if (ip0 == 10) {
                counts[6]++;
            } else if (ip0 == 172 && ip1 >= 16 && ip1 <= 31) {
                counts[6]++;
            } else if (ip0 == 192 && ip1 == 168) {
                counts[6]++;
            }


        }
        System.out.print(counts[0] + " " + counts[1] + " " + counts[2] + " " + counts[3] + " " + counts[4] + " " + counts[5] + " " + counts[6]);
    }
    private static String toBinary(int n) {
        String binary = Integer.toBinaryString(n);
        for (int i = 0; i < 8 - binary.length(); i++) {
            binary = "0" + binary;
        }
        return binary;
    }
}