题解 | #10进制 VS 2进制#

//错误重现：string ten="0";//!!!!!!!这个地方一定要赋值，不然ten后续[]操作都为空


//掌握字符串各种进制的转换
#include <iostream>
#include <vector>
//#include <cmath>
using namespace std;

string Divide(string str,int x)//字符串除x操作
{
    int remainder=0;
    for(int i=0;i<str.size();i++)
    {
        int current=str[i]-'0'+remainder*10;
        str[i]=current/x+'0';
        remainder=current%x;
    }
    int i=0;
    while(str[i]=='0')
    {
        i++;
    }
    return str.substr(i);
}
string Multiply(string str,int x )//字符串乘x
{
    int cf=0;//进位
    for(int i=str.size()-1;i>=0;i--)
    {
        int current=cf+(str[i]-'0')*x;
        str[i]=current%10+'0';
        cf=current/10;
    }
    if(cf==1)
    str="1"+str;
    return str;
}

string Add(string str,int x)//字符串加x
{
    int cf=x;//个位的进位就是要加的数x
    for(int i=str.size()-1;i>=0;i--)
    {
        int current=str[i]-'0'+cf;
        str[i]=current%10+'0';
        cf=current/10;
    }
    if(cf==1)
    str="1"+str;
    return str;
}

int main() {
    string str;
    while(cin>>str)
    {
        vector<int> binary;//从前往后就是逆序二进制字符串
        while(str.size()!=0)
        {
            binary.push_back((str[str.size()-1]-'0')%2);
            str=Divide(str,2);
        }
        string answer="0";//十进制串
        for(int i=0;i<binary.size();i++)
        {
            answer=Multiply(answer,2);
            answer=Add(answer,binary[i]);
        }
	    cout<<answer<<endl;   
    }
	return 0;
}