小紫书 4-5 UVA 1590 IP Networks

题解：

代码：

#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <algorithm>
using namespace std;
int m, n = 32;
bool net[32], add[32];
void str_to_add(char str[20], int x)
{
	for (int i = 0, j = 0, tmp = 0; j < 20; ++i)
	{
		if (str[i] >= '0'&&str[i] <= '9')
			tmp = tmp * 10 + str[i] - '0';
		else if (str[i] == '.')
		{
			for (int k = 0; k < 8; ++k)
			{
				if (tmp&(1 << k))
					add[j * 8 + 7 - k] = 1;
			}
			tmp = 0; ++j;
		}
		else if (str[i] == 0)
		{
			for (int k = 0; k < 8; ++k)
			{
				if (tmp&(1 << k))
					add[j * 8 + 7 - k] = 1;
			}
			tmp = 0; break;
		}
	}
}
int main()
{
	//freopen("input.txt", "r", stdin);
	char str[20];
	while (scanf("%d", &m) != EOF)
	{
		n = 32;
		for (int i = 0; i < m; ++i)
		{
			memset(add, 0, sizeof(add));
			memset(str, 0, sizeof(str));
			scanf("%s", str);
			str_to_add(str, i);
			if (i == 0)
			{
				for (int j = 0; j < 32; ++j)
					net[j] = add[j];
			}
			else
			{
				for (int j = 0; j < n; ++j)
					if (net[j] != add[j])
					{
						n = j;
						for (int k = n; k < 32; ++k)
							net[k] = 0;
						break;
					}
			}
		}
		int net1[4] = { 0 }, mask[4] = { 0 };
		for (int i = 0; i < 32; ++i)
			net1[i / 8] = net1[i / 8] * 2 + net[i];
		for (int t = n, i = 0; t > 0; ++i)
		{
			if (t >= 8)
				mask[i] = 255;
			else
				mask[i] = 255 - ((1 << (8 - t)) - 1);
			t -= 8;
		}
		for (int i = 0; i < 4; ++i)
		{
			printf("%d", net1[i]);
			if (i == 3)
				printf("\n");
			else
				printf(".");
		}
		for (int i = 0; i < 4; ++i)
		{
			printf("%d", mask[i]);
			if (i == 3)
				printf("\n");
			else
				printf(".");
		}
	}
	//system("pause");
	//while (1);
	return 0;
}