题解 | #判断两个IP是否属于同一子网#

#include<iostream>
#include<string>
#include<vector>
using namespace std;
vector<int> ipValue(const string& str);
bool ipIsValid(const vector<int>& p);
bool ipIsValidMask(const vector<int>& p);
int ipIsSame(const vector<int>& p1, const vector<int>& p2, const vector<int>& m);
int main(){
    string ip1;
    string ip2;
    string mask;
    while(cin >> mask >> ip1 >> ip2){
        vector<int>p1 = ipValue(ip1);
        vector<int>p2 = ipValue(ip2);
        vector<int>m = ipValue(mask);
        if(!ipIsValid(p1) || !ipIsValid(p2) || !ipIsValidMask(m)){
            //cout <<ipIsValidMask(m) << endl;
            cout << 1 << endl;
        }else{
            cout << ipIsSame(p1, p2, m) << endl;
        }
    }
    return 0;
}
vector<int> ipValue(const string& str){
    int i = 0;
    int num = 0;
    vector<int> p;
    while(i < str.size()){
        if(str[i] == '.'){
            p.push_back(num);
            num = 0;
        }else if(i == str.size() - 1){
            num = num * 10 + (str[i] - '0');
            p.push_back(num);
        }else{
            num = num * 10 + (str[i] - '0');
        }
        i++;
    }
    return p;
}

bool ipIsValid(const vector<int>& p){
    for(int i = 0; i < p.size(); ++i){
        if(p[i] > 255 || p[i] < 0)
            return false;
    }
    return true;
}
bool ipIsValidMask(const vector<int>& p){
    for(int i = 0; i < p.size(); ++i){
        if(p[i] > 255 || p[i] < 0)
            return false;
        if(p[i]>0&&p[i-1]<255&&i>0)
            return false;
    }
    return true;
}

int ipIsSame(const vector<int>& p1, const vector<int>& p2, const vector<int>& m){
    int flag = 0;
    for(int i = 0; i < p1.size(); ++i){
        int a = p1[i] & m[i];
        int b = p2[i] & m[i];
        if(a != b){
            return 2;
        }
    }
    return 0;
}