题解 | #判断两个IP是否属于同一子网#

#include <iostream>
using namespace std;
#include <string>
#include <sstream>

unsigned str2us(string str) {
    string num;
    unsigned b;
    istringstream bmCode(str);
    while (getline(bmCode, num, '.')) {
        b = (b << 8) + stoi(num);
    }
    return b;
}


bool ipScan(string str) {
    string num;
    istringstream is(str);
    while (getline(is, num, '.')) {
        if (stoi(num) > 255 || stoi(num) < 0) {
            return false;
        }
    }
    return true;
}

bool bmScan(unsigned b) {
    if (!b) {
        return false;
    }
    b = ~b + 1;
    if (b == 1) {
        return false;
    }

    if ((b & (b - 1)) == 0) {
        return true;
    }
    return false;
}

int main() {
    string bmCode;
    string ip1;
    string ip2;
    getline(cin, bmCode);
    getline(cin, ip1);
    getline(cin, ip2);
    unsigned bm = str2us(bmCode);
    if (!ipScan(ip1) || !ipScan(ip2) || !bmScan(bm)) {
        cout << "1" << endl;
        return 0;
    }

    unsigned uip1 = str2us(ip1);
    unsigned uip2 = str2us(ip2);

    unsigned result1 = uip1 & bm;
    unsigned result2 = uip2 & bm;
    if (result1 == result2) {
        cout << "0" << endl;
    } else {
        cout << "2" << endl;
    }

}

https://www.nowcoder.com/discuss/459763190767869952?sourceSSR=users

基本上复用HJ18的代码就ok了

主要还是对子网掩码是否合法的判断，还有地址向数字的判断