进制转换 16-8

先贴出自己写的代码：

#include<iostream>
#include<string> 
#include<map>
using namespace std;

string dbit;

map<string,string> map_bit_hex;

void deal_map()//2进制转八进制，STL中map的运用，以这种写法主要为了熟悉其掌握。
{
	map_bit_hex["000"] = "0";
	map_bit_hex["001"] = "1";
	map_bit_hex["010"] = "2";
	map_bit_hex["011"] = "3";
	map_bit_hex["100"] = "4";
	map_bit_hex["101"] = "5";
	map_bit_hex["110"] = "6";
	map_bit_hex["111"] = "7";
}


void my_strcpy(int j, string &strs, const char *bits) {
	if (j == 0) {
		int i = 0, k = 0;
		while (bits[i] == '0') {
		i++;
		}
		strs.append(bits+i);
		
	} 
	else {
		
		strs.append(bits);
		}
	
}

void hex_bit(string &hex)
{
	int j;
	dbit = "";
	for (j = 0; j < hex.length(); j++) {

		switch (hex[j]) {
		case '0':
		my_strcpy(j, dbit, "0000");
		break;
		case '1':
		my_strcpy(j, dbit, "0001");
		break;
		case '2':
		my_strcpy(j, dbit, "0010");
		break;
		case '3':
		my_strcpy(j, dbit, "0011");
		break;
		case '4':
		my_strcpy(j, dbit, "0100");
		break;
		case '5':
		my_strcpy(j, dbit, "0101");
		break;
		case '6':
		my_strcpy(j, dbit, "0110");
		break;
		case '7':
		my_strcpy(j, dbit, "0111");
		break;
		case '8':
		my_strcpy(j, dbit, "1000");
		break;
		case '9':
		my_strcpy(j, dbit, "1001");
		break;
		case 'A':
		my_strcpy(j, dbit, "1010");
		break;
		case 'B':
		my_strcpy(j, dbit, "1011");
		break;
		case 'C':
		my_strcpy(j, dbit, "1100");
		break;
		case 'D':
		my_strcpy(j, dbit, "1101");
		break;
		case 'E':
		my_strcpy(j, dbit, "1110");
		break;
		case 'F':
		my_strcpy(j, dbit, "1111");
		break;
		}
	}
}

void bit_oct_print()
{
	int apply;

	
	apply = dbit.length()%3;
	if(apply == 0)//补位。这是一个重点，使其为三的倍数
	{
	}
	else if(apply == 1)
	{
		dbit.insert(0,"00");//可以写成 dbit = "00" + dbit
	}
	else if(apply == 2)
	{
		dbit.insert(0,"0");
	}
	else{cout << "error 1";}

	int p = 0;
	while(p*3 != dbit.size())
	{
		string temp;
		temp = string(dbit,p*3,3);
		cout  << map_bit_hex[temp];
		p++;
		
	}
	putchar(10);
}
int main()
{
	int linenum;
	int i;
	deal_map(); 
	string hex_data[10];
    cin >> linenum;
    for(i = 0;i < linenum;i++)
    {
        cin  >> hex_data[i];
	}
	for(i = 0;i < linenum;i++)
	{
		hex_bit(hex_data[i]);
		bit_oct_print();
	}
	

	system("pause");
	return 0;
}

自己的代码有点冗长，主要因为在处理八进制转二进制没有用更好的办法。

以下是别人的代码。

#include <iostream>  
#include <string>  
using namespace std;  
  
int main()  
{  
    int n;  
    cin>>n;  
    for(int k=1;k<=n;k++)  
    {  
        string s1,s2;//s1为输入的原始的十六进制串，s2为转化成的二进制串  
        cin>>s1;  
        s2="";//初始化  
        for(int i=0;i<s1.length();i++)//遍历，字符串上加上每一位  
        {  
            switch(s1[i])  
            {  
                case '0':s2+="0000";break;  
                case '1':s2+="0001";break;  
                case '2':s2+="0010";break;  
                case '3':s2+="0011";break;  
                case '4':s2+="0100";break;  
                case '5':s2+="0101";break;  
                case '6':s2+="0110";break;  
                case '7':s2+="0111";break;  
                case '8':s2+="1000";break;  
                case '9':s2+="1001";break;  
                case 'A':s2+="1010";break;  
                case 'B':s2+="1011";break;  
                case 'C':s2+="1100";break;  
                case 'D':s2+="1101";break;  
                case 'E':s2+="1110";break;  
                case 'F':s2+="1111";break;  
                default:break;  
            }  
        }  
        int len=s2.length();  
  
        if(len%3==1)//三个二进制为一位八进制，二进制串前面补0，确保二进制串的长度为3的倍数  
            s2="00"+s2;  
        else if(len%3==2)  
            s2="0"+s2;  
        int flag=0;  
        for(int i=0;i<=s2.length()-3;i+=3)  
        {  
            int num=4*(s2[i]-'0')+2*(s2[i+1]-'0')+(s2[i+2]-'0');  
            if(num)  
                flag=1;//忽略前导0  
            if(flag)  
                cout<<num;  
        }  
        cout<<endl;  
    }  
    return 0;  
}  

map参考来源：https://www.cnblogs.com/fnlingnzb-learner/p/5833051.html