基础练习 16进制转8进制

在2-8进制转换时注意后三位处理即可

#include <iostream>
#include <string>
using namespace std;
int main()
{
    int n,i;
    cin>>n;
    while(n--)
     {    
         int num=0;
         string a="",b;
        cin>>a;
        b="";
        for(i=0;i<a.length();i++)
        {
            switch(a[i])
            {
                case '0':b+="0000";break;
                case '1':b+="0001";break;
                case '2':b+="0010";break;
                case '3':b+="0011";break;
                case '4':b+="0100";break;
                case '5':b+="0101";break;
                case '6':b+="0110";break;
                case '7':b+="0111";break;
                case '8':b+="1000";break;
                case '9':b+="1001";break;
                case 'A':b+="1010";break;
                case 'B':b+="1011";break;
                case 'C':b+="1100";break;
                case 'D':b+="1101";break;
                case 'E':b+="1110";break;
                case 'F':b+="1111";break;
                default:break;
            }
        }
        int flag=0;
         if(b.length()%3==1){
            b.insert(0,"00");
        }else if(b.length()%3==2){
            b.insert(0,"0");
        }
        for(i=0;i<=b.length()-3;i+=3){
            num=4*(b[i]-'0')+2*(b[i+1]-'0')+(b[i+2]-'0');
            if(num)    
                flag=1;
            if(flag) 
                cout<<num;
        }    
        cout<<endl;
    }
}