Binary to Decimal and Decimal to Binary conversion

Here is a short code for Binary to Decimal Conversion-

int to_dec(string str)
{
    int num=0,i;
    int mask=1;

    for(i=str.length()-1;i>=0;i--)
    {
        if(str.at(i)=='1')
            num|=mask;
        mask<<=1;
    }

        cout << num << endl;
    
    return num;
}

And a short code for Decimal to Binary Conversion-

string to_bin(int num)
{
    string str="";
    int mask=1;

    while(num)
    {
        if(num&mask)
            str="1"+str;
        else
            str="0"+str;

        num>>=1;
    }

    cout << str << endl;
    return str;
}