题解 | #识别有效的IP地址和掩码并进行分类统计#

#include <iostream>
#include <string>
#include <sstream>
#include <vector>
#include <regex>
using namespace std;
vector<string> split(string line,char p);
bool isValidIp(string ip);
bool isValidMask(string mask);
int InClass(string ip);
bool isPriIp(string ip);
int main(){
    string line;
    int countA=0,countB=0,countC=0,countD=0,countE=0,countErr=0,countPri=0;
    while(getline(cin,line)){
        if (line.empty()) {  
            break;
        }
        vector<string> parts;
        parts = split(line,'~');
        if(parts.size()!=2){
            countErr++;
            continue;
        }
        if(!isValidIp(parts[0])){
            countErr++;
            continue;
        }
        if(stoi(split(parts[0],'.')[0])==127||stoi(split(parts[0],'.')[0])==0) continue;
        if(!isValidMask(parts[1])){
            countErr++;
            continue;
        }
        int classNum = InClass(parts[0]);
        switch (classNum) {
            case 1:countA ++;break;
            case 2:countB ++;break;
            case 3:countC ++;break;
            case 4:countD ++;break;
            case 5:countE ++;break;
        }
        if(isPriIp(parts[0])){
            countPri++;
        }
    }
    cout<<countA<<" "<<countB<<" "<<countC<<" "<<countD<<" ";
    cout<<countE<<" "<<countErr<<" "<<countPri<<endl;
    return 0;
}
vector<string> split(string line,char p){
    stringstream ss(line);
    string str1;
    vector<string> parts;
    while(getline(ss,str1,p)){
        parts.push_back(str1);
    }
    return parts;
}
bool isValidIp(string ip){
    regex pattern(R"(^((25[0-5]|2[0-4][0-9]|[0-1]?[0-9]?[0-9])\.){3}(25[0-5]|2[0-4][0-9]|[0-1]?[0-9]?[0-9])$)");
    return regex_match(ip,pattern);
}
bool isValidMask(string mask){
    if(!isValidIp(mask)) return false;
    vector<string> parts = split(mask,'.');
    int maskNum=0;
    for(int i=0;i<3;i++){
        maskNum += stoi(parts[i]);
        maskNum <<= 8;
    }
    maskNum += stoi(parts[3]);
    if(maskNum==0x00000000||maskNum==0xffffffff) return false;
    bool foundZero = false;
    for(int i=31;i>=0;i--){
        if((maskNum & (1<<i))==0){
            foundZero=true;
        }
        else if(foundZero) return false;
    }
    return true;
}
int InClass(string ip){
    vector<string> parts;
    parts = split(ip,'.');
    int a= stoi(parts[0]);
    if(a>=1&&a<=126){
        return 1;
    }
    if(a>=128&&a<=191){
        return 2;
    }
    if(a>=192&&a<=223){
        return 3;
    }
    if(a>=224&&a<=239){
        return 4;
    }
    if(a>=240&&a<=255){
        return 5;
    }
    else return 0;
}
bool isPriIp(string ip){
    vector<string> parts;
    parts = split(ip,'.');
    int a= stoi(parts[0]);
    int b= stoi(parts[1]);
    if((a==10)||(a==172&&b>=16&&b<=31)||(a==192&&b==168))
        return true;
    else return false;
}