题解 | #HJ33 整数与IP地址间的转换#
整数与IP地址间的转换
https://www.nowcoder.com/practice/66ca0e28f90c42a196afd78cc9c496ea
import java.util.*;
public class Main {
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
while (in.hasNextLine()) {
String s = in.nextLine();
if (s.contains(".")) {
System.out.println(ipToNum(s));
} else {
System.out.println(NumToIp(s));
}
}
}
//ip -> num
public static long ipToNum(String ip) {
String[] split = ip.split("\\.");
long result = 0;
//将数字做位运算再累加起来，注意使用long
for (int i = 0; i < split.length; i++) {
long num = Long.parseLong(split[i]);
result += num << (split.length - 1 - i) * 8;
}
return result;
}
//num -> ip
public static String NumToIp(String s) {
long num = Long.parseLong(s);
StringBuffer sb = new StringBuffer();
for (int i = 3; i >= 0; i--) {
sb.append(num / (1 << 8 * i) % 256);
sb.append(".");
}
String result = sb.toString();
return result.substring(0, result.length() - 1);
}
}
查看8道真题和解析