题解 | #识别有效的IP地址和掩码并进行分类统计#

#include <iostream>
#include <istream>
#include <sstream>
#include <string>
#include<bits/stdc++.h>
#include <regex>
#include<cstring>
#include <bitset>
#include <stdlib.h>
#include <vector>
using namespace std;
bool judge_ip(string ip)
{
    string n;
    int number;
    istringstream ss(ip);
    int i=0;
    while(getline(ss,n,'.'))
    {
        i++;
        if(n.empty()) return false;
        number=stoi(n);
        if(number>255||number<0) return false;
    }
    if(i!=4) return false;
    return true;
}

bool judge_mask(string mask)
{
    string n;
    unsigned number=0;
    istringstream ss(mask);
    int i=0;
    while(getline(ss,n,'.'))
    {
        i++;
        if(n.empty()) return false;
        number=(number<<8)+stoi(n);
    }
    if(!number) return false;
    number=~number+1;
    if(number==1) return false;
    if(number&(number-1)) return false;
    if(i!=4) return false;
    return true;
}

bool judge_private(string ip)
{
    string n;
    int number;
    istringstream ss(ip);
    int i=0;
    vector<int> v(4,0);
    while(getline(ss,n,'.'))
    {
        if(n.empty()) return false;
        number=stoi(n);
        if(number>255||number<0) return false;
        v[i]=number;
        i++;
    }
    if(i!=4) return false;
    if(v[0]==10) return true;
    else if(v[0]==172&&v[1]>=16&&v[1]<=31) return true;
    else if(v[0]==192&&v[1]==168) return true;
    return false;
}
int main() {
    string line;
    string ip,mask;
    int a=0,b=0,c=0,d=0,e=0;
    int err=0,pri=0;
    while(getline(cin,line))
    {
        int pos=line.find('~');
        ip=line.substr(0,pos);
        mask=line.substr(pos+1,line.size());
        string head=ip.substr(0,ip.find('.'));
        if(stoi(head)==0||stoi(head)==127) ;
        else if(!judge_mask(mask)) err++;
        else if(!judge_ip(ip)) err++;
        else 
        {
        if(judge_private(ip)) pri++;
        if(stoi(head)>=1&&stoi(head)<=126) a++;
        else if(stoi(head)>=128&&stoi(head)<=191) b++;
        else if(stoi(head)>=192&&stoi(head)<=223) c++;
        else if(stoi(head)>=224&&stoi(head)<=239) d++;
        else if(stoi(head)>=240&&stoi(head)<=255) e++;
        }
    }
    cout<<a<<" "<<b<<" "<<c<<" "<<d<<" "<<e<<" "<<err<<" "<<pri;
}
// 64 位输出请用 printf("%lld")