题解 | 整数与IP地址间的转换

#include<bits/stdc++.h>
using namespace std;
#define IOS ios_base::sync_with_stdio(false);cin.tie(nullptr)
#define INF 0x7fffffff
#define inf 0x3f3f3f3f
#define PII pair<int,int>
#define endl '\n'
#define int long long
#define mod 998244353
#define MOD 1e9+7
int read() {
    char act = 0;
    int f = 1, x = 0;
    while (act = getchar(), act < '0' && act != '-');
    if (act == '-') f = -1, act = getchar();
    x = act - '0';
    while (act = getchar(), act >= '0') x = x * 10 + act - '0';
    return x * f;
}
int quick_pow(int base, int pow){
    int res=1;
    while(pow){
        if(pow&1)res*=base;
        base*=base;
        pow>>=1;
    }
    return res;
}
void solve() {
  	//暴力拆解
    string s;
    cin >> s;
    int n;
    cin >> n;
    vector<string>a;
    while (s.find('.') != -1) {
        int pos = s.find('.');
        string temp = s.substr(0, pos);
        a.push_back(temp);
        s = s.substr(pos + 1);
    }
    a.push_back(s);
    string ans = "";
    for (auto i : a) {
        int temp = stol(i);
        string tt = "";
        while (temp) {
            int x = temp % 2;
            string ss = to_string(x);
            tt += ss;
            temp /= 2;
        }
        reverse(tt.begin(), tt.end());
        if(s.size()<8){
            int cnt=8-tt.size();
            for(int i=1;i<=cnt;i++){
                tt="0"+tt;
            }
        }
        //cout<<tt<<endl;
        ans += tt;
    }
    int sum=0;
    //cout<<ans<<endl;
    reverse(ans.begin(),ans.end());
    for(int i=0;i<ans.size();i++){
        if(ans[i]=='0')continue;
        sum+=quick_pow(2,i);
    }
    cout<<sum<<endl;
    string res="";
    while(n){
        res+=to_string(n%2);
        n/=2;
    }
    reverse(res.begin(),res.end());
    if(res.size()<32){
        int cnt=32-res.size();
        for(int i=1;i<=cnt;i++){
            res="0"+res;
        }
    }
    string s1,s2,s3,s4;
    s1=res.substr(0,8);
    s2=res.substr(8,8);
    s3=res.substr(16,8);
    s4=res.substr(24);
    //cout<<s1<<" "<<s2<<" "<<s3<<" "<<s4<<endl;
    vector<int>num(5,0);
    reverse(s1.begin(),s1.end());
    reverse(s2.begin(),s2.end());
    reverse(s3.begin(),s3.end());
    reverse(s4.begin(),s4.end());
    for(int i=0;i<8;i++){
        if(s1[i]=='1')num[1]+=quick_pow(2,i);
        if(s2[i]=='1')num[2]+=quick_pow(2,i);
        if(s3[i]=='1')num[3]+=quick_pow(2,i);
        if(s4[i]=='1')num[4]+=quick_pow(2,i);
    }
    for(int i=1;i<=4;i++){
        if(i!=4)cout<<num[i]<<".";
        else cout<<num[i]<<endl;
    }
}
signed main() {
    IOS;
    int t = 1;
    //cin>>t;
    while (t--) {
        solve();
    }

    return 0;
}