zoj2482 IP Address（水题，但有个语法想不通）

IP Address

Time Limit: 2000MS Memory Limit: 65536KB 64bit IO Format: %lld & %llu

Submit Status

Description

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:

2⁷2⁶2⁵2⁴2³2²2¹2⁰1286432168421

Input

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.

Output

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.

Sample Input

4
00000000000000000000000000000000
00000011100000001111111111111111
11001011100001001110010110000000
01010000000100000000000000000001

Sample Output

0.0.0.0
3.128.255.255
203.132.229.128
80.16.0.1

Source

Mexico and Central America 2004

 

 

 

 

分析：

水题。但有个语法问题想不通。cin>>c才能配合c-='0'这种用法。但不知道为什么？？？？

ac代码：

#include <iostream>
#include<cstdio>
using namespace std;

int main()
{
    int pos[8]={128,64,32,16,8,4,2,1};//顺序反过来
    char c;
    int n,i,j;
    int sum;
    scanf("%d",&n);
    while(n--)
    {
        for(i=0;i<4;i++)
        {
             sum=0;
            for(j=0;j<8;j++)
            {
                //scanf("%c",&c);//cin>>c才能配合c-='0'这种用法。但不知道为什么？？？？
                cin>>c;
                //c-='0';//记住这种用法,此时c转换为int型.或c-=48;
                c-=48;
                if(c)//此时c转换为int型
                sum+=pos[j];
            }
            if(i)
            printf(".");
            printf("%d",sum);
        }
        printf("\n");
    }
    return 0;
}