POJ 2105 / México and Central America 2004 IP Address (strtoll函数)_c++閲孧茅xico and central america 2004-优快云博客

本文链接：https://blog.youkuaiyun.com/synapse7/article/details/13021649

本文详细介绍了如何将32位的二进制IP地址序列转换为点分十进制格式的方法，包括使用标准库中的`strtoll`函数实现这一过程。通过分组8位进行转换，最终输出完整的IP地址。

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IP Address

http://poj.org/problem?id=2105

Time Limit: 1000MS

Memory Limit: 30000K

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:

2⁷   2⁶  2⁵  2⁴  2³   2²  2¹  2⁰ 

128 64  32  16  8   4   2   1

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

México and Central America 2004

这题可以直接算，也可以用一个cstdlib中的strtoll函数搞定

完整代码：

/*0ms,408KB*/

#include<cstdio>
#include<cstdlib>

char str[40];
int ip[4];

int main()
{
	char* stopstr;
	__int64 num;
	int t, i;
	scanf("%d\n", &t);
	while (t--)
	{
		gets(str);
		num = strtoll(str, &stopstr, 2);
		for (i = 3; i >= 0; --i)
		{
			ip[i] = num % 256;
			num >>= 8;
		}
		printf("%d.%d.%d.%d\n", ip[0], ip[1], ip[2], ip[3]);
	}
	return 0;
}