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2013
11-10

POJ 2105 IP Address [解题报告] Java

IP Address

问题描述 :

Suppose you are reading byte streams from any device, representing IP addresses. Your task is to convert a 32 characters long sequence of ’1s’ and ’0s’ (bits) to a dotted decimal format. A dotted decimal format for an IP address is form by grouping 8 bits at a time and converting the binary representation to decimal representation. Any 8 bits is a valid part of an IP address. To convert binary numbers to decimal numbers remember that both are positional numerical systems, where the first 8 positions of the binary systems are:
27   26  25  24  23   22  21  20 

128 64 32 16 8 4 2 1

输入:

The input will have a number N (1<=N<=9) in its first line representing the number of streams to convert. N lines will follow.

输出:

The output must have N lines with a doted decimal IP address. A dotted decimal IP address is formed by grouping 8 bit at the time and converting the binary representation to decimal representation.

样例输入:

4
00000000000000000000000000000000 
00000011100000001111111111111111 
11001011100001001110010110000000 
01010000000100000000000000000001 

样例输出:

0.0.0.0
3.128.255.255
203.132.229.128
80.16.0.1

解题代码:

import java.util.*;   
  
public class Main {   
  
    public static void main(String[] args) {   
        Scanner cin = new Scanner(System.in);   
           
        int num = Integer.valueOf(cin.nextLine()).intValue();   
  
  
           
        for(int i = 0; i < num; i++)   
        {   
            String str, temp;   
            int a,b,c,d = 0;   
            StringBuffer sb = new StringBuffer();   
               
            str = cin.nextLine();   
            temp = str.substring(0, 8);   
            sb.append(convert(temp));   
            sb.append('.');   
            temp = str.substring(8, 16);   
            sb.append(convert(temp));   
            sb.append('.');   
            temp = str.substring(16, 24);   
            sb.append(convert(temp));   
            sb.append('.');   
            temp = str.substring(24);   
            sb.append(convert(temp));   
  
            System.out.println(sb.toString());   
        }   
  
    }   
       
    private static int convert(String str)   
    {   
        int value = 0;   
        if(str.charAt(0) == '1')   
            value += 128;   
        if(str.charAt(1) == '1')   
            value += 64;   
        if(str.charAt(2) == '1')   
            value += 32;   
        if(str.charAt(3) == '1')   
            value += 16;   
        if(str.charAt(4) == '1')   
            value += 8;   
        if(str.charAt(5) == '1')   
            value += 4;   
        if(str.charAt(6) == '1')   
            value += 2;   
        if(str.charAt(7) == '1')   
            value += 1;   
           
        return value;   
    }   
  
}

  1. “再把所有不和该节点相邻的节点着相同的颜色”,程序中没有进行不和该节点相邻的其他节点是否相邻进行判断。再说求出来的也不一样是颜色数最少的

  2. 第一题是不是可以这样想,生了n孩子的家庭等价于n个家庭各生了一个1个孩子,这样最后男女的比例还是1:1