二进制转十六进制

string binToHex(string bin){
    string hex="";
    if(bin.size()%4!=0){
        for(int i=0;i<(4-bin.size()%4);i++){
            bin="0"+bin;
        }
    }
    for(int i=0;i<bin.size();i+=4){
        string tmp=bin.substr(i,4);
        bitset<4>b(tmp);
        hex+=b.to_ulong()<10?char(b.to_ulong()+'0'):char(b.to_ulong()+'A'-10);

    }
    return hex;
}

十六进制转二进制

string hexToBin(string hex){
    bitset<8>s(stoi(hex,nullptr,16));
    return s.to_string();
}

测试demo

#include <iostream>
#include<sstream>
#include<cstring>
#include<cctype>
#include<bitset>
using namespace std;

string binToHex(string bin){
    string hex="";
    if(bin.size()%4!=0){
        for(int i=0;i<(4-bin.size()%4);i++){
            bin="0"+bin;
        }
    }
    for(int i=0;i<bin.size();i+=4){
        string tmp=bin.substr(i,4);
        bitset<4>b(tmp);
        hex+=b.to_ulong()<10?char(b.to_ulong()+'0'):char(b.to_ulong()+'A'-10);

    }
    return hex;
}

string hexToBin(string hex){
    bitset<8>s(stoi(hex,nullptr,16));
    return s.to_string();
}
int main() {
    string str="FF";
    cout<<"hex is : "<<str<<endl;
    cout<<"hexToBin: ";
    cout<<hexToBin(str)<<endl;
    cout<<"binToHex: ";
    cout<<binToHex(hexToBin(str))<<endl;


    return 0;
}

运行结果

十进制转二进制

long long  decToBin(int dec){
	long long   res = 0, j = 1;
	while(dec){
		res = res + j * (dec % 2);
		dec = dec / 2;
		j = j * 10;
	}
	return res;
}

二进制转十进制

int binToDec(string str){
    int res=0;
    for(int i=0;i<str.size();i++){
        int num=str[i]-'0';
        res=res*2+num;
    }
    return res;
}

测试demo

#include <iostream>
#include<sstream>
#include<cstring>
#include<cctype>
using namespace std;

long long  decToBin(int dec){
	long long   res = 0, j = 1;
	while(dec){
		res = res + j * (dec % 2);
		dec = dec / 2;
		j = j * 10;
	}
	return res;
}

int binToDec(string str){
    int res=0;
    for(int i=0;i<str.size();i++){
        int num=str[i]-'0';
        res=res*2+num;
    }
    return res;
}
int main() {
    int num;
    while (cin >>num) { 
        cout<<"num is : "<<num<<endl;
        cout<<"decToBin: ";
        cout<<decToBin(num)<<endl;
        cout<<"binToDec: ";
        cout<<binToDec(to_string(decToBin(num)))<<endl;
         
    }
    return 0;
}

测试结果