题解 | #识别有效的IP地址和掩码并进行分类统计#

import java.io.;
import java.util.;

public class Main {
public static void main(String[] args) throws IOException {
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
int a = 0, b = 0, c = 0, d = 0, e = 0, err = 0, pri = 0;
String str;
while((str = br.readLine()) != null) {
int index = str.indexOf('~');
long ip = ipToNum(str.substring(index + 1));
if(ip <= 0 || ip >=0XFFFFFFFFL || (((ip ^ 0XFFFFFFFFL) + 1) | ip)!= ip)
{
err += 1;
continue;
}
ip = ipToNum(str.substring(0, index));
long partOfIP = ip >> 24;
if(ip <= 0L || ip >= 0XFFFFFFFFL) {
err += 1;
} else if(partOfIP >= 1 && partOfIP <= 126) {
a += 1;
if(partOfIP == 10) {
pri += 1;
}
} else if(partOfIP >= 128 && partOfIP <= 191) {
b += 1;
if(ip >> 20 == 0XAC1) {
pri += 1;
}
} else if(partOfIP >= 192 && partOfIP <= 223) {
c += 1;
if(ip >>16 == 0XC0A8) {
pri += 1;
}
} else if(partOfIP >= 224 && partOfIP <= 239) {
d += 1;
} else if(partOfIP >= 240 && partOfIP <= 255) {
e += 1;
}
}
System.out.println(a + " " + b + " " + c + " " + d + " " + e + " "
+ err + " " + pri);
}
public static long ipToNum(String ip) {
long num = 0;
int flag = 1, temp = 0;
char[] chars = ip.toCharArray();
for(int i = 0; i < chars.length; i++) {
if(chars[i] == '.') {
num = num << 8 | temp;
temp = 0;
flag ++;
continue;
}
if(flag >= 2) {
return -1;
}
if(chars[i] >= '0' && chars[i] <= '9') {
temp = temp * 10 + chars[i] - '0';
flag = 0;
}
else {
flag = 3;
break;
}
}
if(flag >= 2) {
return -1;
}
num = num << 8 | temp;
return num;
}
}