题解 | #判断两个IP是否属于同一子网#

思路很简单，细节需要注意，方法比较笨，代码又臭又长，继续向大佬学习，看了下别人的代码，子码掩码的判断直接看255和0，这个比较不用像我写了一大堆转化为二进制字符串再和1比较

#include <sstream>
#include <string>
#include <vector>
#include <bitset>
using namespace std;
//整数转化字符串
string interToString(int num) {
	stringstream s;
	s << num;
	return s.str();
}
//大于0的整数二进制数转化
string transparentIp(int num)
{
	string result = "";
	if (num == 0)
		result = "00000000";
	while (num > 0) {
		result = char((num % 2) + '0') + result;
		num = num / 2;
	}
	if (result.size() < 8) {
		string tmp_s (8 - result.size(), '0');
		result = tmp_s + result;
	}
	return result;
}
//字码掩码校验
bool checkZm(vector<int> intIpResult)
{
	string ipStr = "";
	for (int i = 0; i < 4; i++) {
		ipStr += transparentIp(intIpResult[i]);
	}
	int find_1_index = ipStr.find_last_of('1');
	string ipStr2(find_1_index + 1, '1');
	if (ipStr2.compare(ipStr.substr(0, find_1_index + 1)) == 0)
		return true;
	else
		return false;
}
//输入的ip字符串进行切分和转化为整数并且判断
bool checkIpStr(string str, vector<int> *intIpResult)
{
	string tmp = "";
	int ipNum = 0, index = 0;
	for (index = 0; index < str.size(); index++) {
		if (str[index] == '.' || index == str.size() - 1) {
			if (index == str.size() - 1) tmp += str[index];
			if (tmp == "." || tmp.empty()) return false;
			ipNum = stoi(tmp);
			if (ipNum > 255 || ipNum < 0)
				return false;
			else
				intIpResult->push_back(ipNum);
			tmp = "";
		}
		else {
			tmp += str[index];
		}
	}
	if (index == str.size())
		return true;
    else
        return false;
}

int main()
{
	string zmStr, ipStr1, ipStr2, tmp1, tmp2;
	vector <int> inAddr;
	while (cin >> zmStr >> ipStr1 >> ipStr2) {
		inAddr.clear();
		tmp1 = tmp2 = "";
		if (checkIpStr(zmStr, &inAddr) && checkIpStr(ipStr1, &inAddr) && checkIpStr(ipStr2, &inAddr)) {
			if (inAddr.size() != 12) {
				cout << 1 << endl;
				continue;
			}
            //增加个单独对字码掩码的校对
			if (!checkZm(inAddr)) {
				cout << 1 << endl;
				continue;
			}
            //ip地址转化为二进制字符串
			for (int i = 0; i < 4; i++) {
			    tmp1 += interToString((inAddr[i] & inAddr[i + 4]));
				tmp2 += interToString((inAddr[i] & inAddr[i + 8]));
			}
			if (tmp1.compare(tmp2) == 0)
				cout << 0 << endl;
			else
				cout << 2 << endl;
		}
		else {
			cout << 1 << endl;
		}
	}
}