题解 | #判断两个IP是否属于同一子网#

话不多说，暴力求解就完事儿了。

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        while (sc.hasNext()) { // 注意 while 处理多个 case
            String s1 = sc.nextLine();
            String ip1 = sc.nextLine();
            String ip2 = sc.nextLine();
            int[]ip00 = getNum(s1);
            int[]ip11 = getNum(ip1);
            int[]ip22 = getNum(ip2);
            if(valid(ip00)&&valid(ip11)&&valid(ip22)){
                int[]ip000 = transform(ip00);
                int flag = 0;
                for(int i =0;i<31;++i){
                    if(ip000[i]==0&&ip000[i+1]==1) {
                        System.out.println(1);
                        flag = 1;
                        break;
                    }

                }
                if(flag==1)continue;
                int[]ip111 = transform(ip11);
                int[]ip222 = transform(ip22);
                if(check(ip000,ip111,ip222)){
                    System.out.println(0);
                }else System.out.println(2);

            }
            else System.out.println(1);
        }
    }
    public static boolean valid000(int []ip){
        for(int i =0;i<31;++i){
            if(ip[i]==0&&ip[i+1]==1)return false;
        }
        return true;
    }
    public static boolean check(int[]ip1,int[]ip2,int[]ip3){
        int [] ipcheck1 = new int[32];
        int []ipcheck2 = new int[32];
        for(int i = 0;i<32;++i){
            ipcheck1[i] = ip1[i]&ip2[i];
            ipcheck2[i] = ip1[i]&ip3[i];
            if(ipcheck1[i]!=ipcheck2[i])return false;
        }
        return true;
    }
    public static int[] transform(int[]ips){
        int index = 0;
        int []res = new int[32];
        for(int i =0;i<ips.length;++i){
            int [] temp = getBit(ips[i]);
            for(int j = 0;j<8;++j){
                res[index++] = temp[j];
            }
        }
        return res;
    }
    public static int[] getBit(int n){
        int res[] = new int[8];
        int index = 7;
        while(n!=0){
            res[index--] = n%2;
            n/=2;
        }
        return res;
    }
    public static boolean valid(int[]ips){
        if(ips.length!=4)return false;
        for(int i:ips){
            if(i>=0&&i<256)continue;
            else return false;
        }
        return true;
    }
    public static int[] getNum(String ip){
        String []ips = ip.split("\\.");
        int []res = new int[ips.length];
        int index = 0;
        for(String s:ips){
            res[index++] = Integer.parseInt(s);
        }
        return res;
    }
}