题解 | #整数与IP地址间的转换#

#include <bits/stdc++.h>

using namespace std;

void process(string strIP, long decIP, long& _decIP, string& _strIP){
    stringstream iss(strIP);
    string sTmp = "";
    vector<long> nums; //long
    while(getline(iss, sTmp, '.')){
        nums.push_back(atol(sTmp.c_str()));
    }
    _decIP = nums[0] << 24 | nums[1] << 16 | nums[2] << 8 | nums[3]; //位运算组装
    
    _strIP += to_string((decIP >> 24) & 0xff); //取第一个八位二进制转换成字符  & 0xff
    _strIP += ".";
    _strIP += to_string((decIP >> 16) & 0xff);
    _strIP += ".";
    _strIP += to_string((decIP >> 8) & 0xff);
    _strIP += ".";
    _strIP += to_string(decIP & 0xff);
}

int main(){
    string strIP = "";
    long decIP = 0;
    cin >> strIP;
    cin >> decIP;
    
    long _decIP = 0;
    string _strIP = "";
    process(strIP, decIP, _decIP, _strIP);
    
    cout << _decIP << endl;
    cout << _strIP <<endl;
    
    return 0;
}