题解 | #整数与IP地址间的转换#

import java.util.Scanner;

/**
 * HJ33 整数与IP地址间的转换
 * @author d3y1
 */
public class Main {
    public static void main(String[] args) {
        // solution1();
        solution2();
    }

    /**
     * 字符串
     */
    private static void solution1(){
        Scanner in = new Scanner(System.in);

        String ipAddr = in.nextLine().trim();
        String ipNumber = in.nextLine().trim();

        System.out.println(ipAddrToNumber(ipAddr));
        System.out.println(ipNumberToAddr(ipNumber));
    }

    /**
     * IP地址 -> 10进制的IP地址
     * 
     * 256进制 -> 2进制 -> 10进制
     * 
     * @param ipAddr
     * @return
     */
    private static String ipAddrToNumber(String ipAddr){
        String[] parts = ipAddr.split("\\.");
        StringBuilder sb = new StringBuilder();
        String binStr;
        int len;
        for(String part: parts){
            binStr = Integer.toBinaryString(Integer.parseInt(part));
            len = binStr.length();
            for(int i=1; i<=8-len; i++){
                sb.append(0);
            }
            sb.append(binStr);
        }

        // Long number = 0L;
        // for(char ch: sb.toString().toCharArray()){
        //     number = (number<<1) + Integer.valueOf(String.valueOf(ch));
        // }

        return String.valueOf(Long.parseLong(sb.toString(), 2));
    }

    /**
     * 10进制的IP地址 -> IP地址
     * 
     * 10进制 -> 2进制 -> 256进制
     * 
     * @param ipNumber
     * @return
     */
    private static String ipNumberToAddr(String ipNumber){
        String binStr = Long.toBinaryString(Long.parseLong(ipNumber));
        int len = binStr.length();
        StringBuilder sb = new StringBuilder();
        for(int i=1; i<=32-len; i++){
            sb.append(0);
        }
        sb.append(binStr);

        StringBuilder ipAddr = new StringBuilder();
        String ipBinStr = sb.toString();
        String part;
        int val;
        for(int i=0; i<32; i+=8){
            part = ipBinStr.substring(i, i+8);
            // val = 0;
            // for(char ch: part.toCharArray()){
            //     val = (val<<1) + Integer.valueOf(String.valueOf(ch));
            // }
            val = Integer.parseInt(part, 2);
            ipAddr.append(val);
            ipAddr.append(".");
        }

        return ipAddr.substring(0, ipAddr.length()-1);
    }

    /**
     * 字符串
     */
    private static void solution2(){
        Scanner in = new Scanner(System.in);

        String ipAddr = in.nextLine().trim();
        String ipNumber = in.nextLine().trim();

        System.out.println(AddrToNumber(ipAddr));
        System.out.println(NumberToAddr(ipNumber));
    }

    /**
     * IP地址 -> 10进制的IP地址
     * 
     * 256进制 -> 10进制 (直接转换 不用经过2进制)
     * 
     * @param ipAddr
     * @return
     */
    private static String AddrToNumber(String ipAddr){
        String[] parts = ipAddr.split("\\.");
        Long number = 0L;
        for(String part: parts){
            number = number*256 + Integer.parseInt(part);
        }

        return String.valueOf(number);
    }

    /**
     * 10进制的IP地址 -> IP地址
     * 
     * 10进制 -> 256进制 (直接转换 不用经过2进制)
     * 
     * @param ipNumber
     * @return
     */
    private static String NumberToAddr(String ipNumber){
        Long number = Long.parseLong(ipNumber);
        StringBuilder sb = new StringBuilder();
        for(int i=1; i<=4; i++){
            sb.insert(0, number%256+".");
            number /= 256;
        }

        return sb.substring(0, sb.length()-1);
    }
}