Cracking the coding interview 5.2

Given a (decimal-e.g. 3.72) number that is passed in as a string, print the binary representation. If the number can not be represented accurately in binary, print "error"

 

Integer:

Take the remainder of 2, move one to the right, and repeat until the integer is 0.

Decimal part:

Multiply by 2 to see if the result is greater than 1. If it is greater than 1, then 2 ^-1 places the upper 1; otherwise, it is 0. If the value is greater than 1, the result is reduced by 1 and then multiplied by 2. Otherwise, the result is multiplied by 2 to continue the judgment until the decimal part exceeds 32 bits, and an error is returned.

For example: 0.75d = 0.11b, multiply by 2 is actually equivalent to shift left. If the result is greater than 1, it means that 2 ^-1 is 1, then subtract 1, continue multiply by 2, and the result is equal to 1, it indicates that 2 ^-2 is 1 and there is no decimal place behind it.

#include<iostream>#include<string>#include<stdlib.h>using namespace std;string func(const string &str){    string strInt;    string strDou;    string::size_type idx = str.find(‘.‘);        if(idx == string::npos)    {        strInt = str;    }    else    {        strInt = str.substr(0,idx);        strDou = str.substr(idx);    }    int intPart = atoi(strInt.c_str());    double douPart;    if(!strDou.empty())    {        douPart = atof(strDou.c_str());    }    else    {        douPart = 0.0;    }    string strIntB,strDouB;    while(intPart!=0)    {        if((intPart&1)>0)        {            strIntB = ‘1‘+strIntB;        }        else        {            strIntB = ‘0‘+strIntB;        }        intPart=intPart>>1;    }    while(!(douPart>-10e-15 && douPart<10e-15))    {        if(douPart*2>1)        {            strDouB = ‘1‘+strDouB;            douPart = douPart*2-1;        }        else if((douPart*2-1)>-10e-15 && (douPart*2-1)<10e-15)        {            strDouB = ‘1‘+strDouB;            break;        }        else        {            strDouB = ‘0‘+strDouB;        }        if(strDouB.size()>32)        {            return "ERROR";        }    }    if(strDouB.empty())    {        return strIntB;    }    else    {        return (strIntB+‘.‘+strDouB);    }}int main(){    string str("3.75");    cout<<func(str)<<endl;    return 0;}