I decided to implement addition using strings, as my numbers may be huge. The problem that I'm facing is how to convert from decimal numbers in strings to binary. If lol is the result of an addition, I'm trying to convert it to a binary form using:
unsigned long long function_arg = atoi( lol.c_str() );
As the number of digits grows, as for example n>14, it fails, so even long long is too short. What can you advise me to do? Here is actually the code of my program (working with decimal system):
#include <iostream>
#include <string>
#include <bitset>
#include <conio.h>
using namespace std;
string add (string &s1, string &s2) {
int carry=0,sum,i;
string min=s1,
max=s2,
result = "";
if (s1.length() > s2.length()) {
max = s1;
min = s2;
} else {
max = s2;
min = s1;
}
for (i = min.length()-1; i>=0; i--) {
sum = min[i] + max[i + max.length() - min.length()] + carry - 2*'0';
carry = sum/10;
sum %=10;
result = (char)(sum + '0') + result;
}
i = max.length() - min.length()-1;
while (i>=0) {
sum = max[i] + carry - '0';
carry = sum/10;
sum%=10;
result = (char)(sum + '0') + result;
i--;
}
if (carry!=0) {
result = (char)(carry + '0') + result;
}
return result;
}
string Dex_To_bin(unsigned long long number){
string result;
unsigned long long bitmask = 1ULL << 63;
do
result.push_back(static_cast<bool>(number & bitmask));
while (bitmask >>= 1);
return result;
}
int main () {
string a,b;
cin >> a >> b;
add(a,b);
cout << add(a,b) << endl;
cout << endl;
cout << endl;
string lol=add(a,b);
unsigned long long funtion_arg = atoi( lol.c_str() );
cout << Dex_To_bin(funtion_arg) << bitset<64>(funtion_arg) << endl;
cin.get();
cin.ignore();
getch();
return 0;
}
Function add works great, the problem is with Dec_to_Bin :(
You're using strings to represent very long numbers, right? Numbers that won't fit into standard numeric types? The result is no different. Think of making a set of functions that take numbers-represented-as-strings. That's the only way they're allowed to deal with the numbers.
So, write your decimal-to-binary function to take the string directly, and convert one digit of the string at a time.
What can you advise me to do?
Don't. A large value can't be converted to a type that is too small. You don't need this method at all in your API, or at least you shouldn't.
BTW the method signature you have devised doesn't make sense. The parameter should have been a 'string', and the result should have been a 'long long'. But don't provide it.
Related
I tried to build a function that calculates a binary number stored in a string into a decimal number stored in a long long. I'm thinking that my code should work but it doesn't.
In this example for the binary number 101110111 the decimal number is 375. But my output is completely confusing.
Here is my code:
#include <string>
#include <stdio.h>
#include <math.h>
#include <iostream>
#include <string.h>
int main() {
std::string stringNumber = "101110111";
const char *array = stringNumber.c_str();
int subtrahend = 1;
int potency = 0;
long long result = 0;
for(int i = 0; i < strlen(array); i++) {
result += pow(array[strlen(array) - subtrahend] * 2, potency);
subtrahend++;
potency++;
std::cout << result << std::endl;
}
}
Here is the output:
1
99
9703
894439
93131255
9132339223
894974720087
76039722530902
8583669948348758
What I'm doing wrong here?
'1' != 1 as mentioned in the comments by #churill. '1' == 49. If you are on linux type man ascii in terminal to get the ascii table.
Try this, it is the same code. I just used the stringNumber directly instead of using const char* to it. And I subtracted '0' from the current index. '0' == 48, so if you subtract it, you get the actual 1 or 0 integer value:
auto sz = stringNumber.size();
for(int i = 0; i < sz; i++) {
result += pow((stringNumber[sz - subtrahend] - '0') * 2, potency);
subtrahend++;
potency++;
std::cout << result << std::endl;
}
Moreover, use the methods provided by std::string like .size() instead of doing strlen() on every iteration. Much faster.
In a production environment, I would highly recommend using std::bitset instead of rolling your own solution:
std::string stringNumber = "1111";
std::bitset<64> bits(stringNumber);
bits.to_ulong();
You're forgetting to convert your digits into integers. Plus you really don't need to use C strings.
Here's a better version of the code
int main() {
std::string stringNumber = "101110111";
int subtrahend = 1;
int potency = 0;
long long result = 0;
for(int i = 0; i < stringNumber.size(); i++) {
result += pow(2*(stringNumber[stringNumber.size() - subtrahend] - '0'), potency);
subtrahend++;
potency++;
std::cout << result << std::endl;
}
}
Subtracting '0' from the string digits converts the digit into an integer.
Now for extra credit write a version that doesn't use pow (hint: potency *= 2; instead of potency++;)
c++ way
#include <string>
#include <math.h>
#include <iostream>
using namespace std;
int main() {
std::string stringNumber = "101110111";
long long result = 0;
uint string_length = stringNumber.length();
for(int i = 0; i <string_length; i++) {
if(stringNumber[i]=='1')
{
long pose_value = pow(2, string_length-1-i);
result += pose_value;
}
}
std::cout << result << std::endl;
}
i know to reverse the digits of a number(integer) in c but my questions is how can we reverse the digits of a real no
for e.g 1200.23 gets reversed as 32.0021
code for integers
#include <stdio.h>
/* Iterative function to reverse digits of num(integer)*/
int reversDigits(int num)
{
int rev_num = 0;
while(num > 0)
{
rev_num = rev_num*10 + num%10;
num = num/10;
}
return rev_num;
}
/*Driver program to test reversDigits*/
int main()
{
int num = 4562;
printf("Reverse of no. is %d", reversDigits(num));
getchar();
return 0;
}
Obviously your paramater needs to be floating point type.
You could convert double to string then reverse the string then convert back to double:
#include <string>
#include <sstream>
template<typename T>
std::string toString(T t)
{
std::stringstream ss;
ss << t;
rteurn ss.str();
}
double reversDigits(double num)
{
std::string s = std::to_string(num);
std::reverse(s.begin(), s.end());
double d;
std::stringstream ss(s);
ss >> d;
return d;
}
You could use the following code, where the iostream library is being used:
#include <iostream>
#include <math.h>
using namespace std;
int main() {
double pass = 0;
double n;
double result=0;
cout << "Please enter a number to reverse" << endl;
cin >> n;
while (trunc(n / pow(10.0, pass)) > 0) {
result = fmod((n / pow(10.0, pass)), 10.0);
cout << trunc(result);
pass = pass + 1;
}
cout << endl;
system("pause");
return 0;
}
This uses the methods (12345/10), which gives you 1234.5 which then truncates into 1234. The above code also use the modulo method ('%' is the operator for modulo). For example, if you do 12345 % 10, the program displays the remainder of 12345/10, which in this case, would be 5.
I used this method in a loop to get the desired output.
PLEASE NOTE THAT I MADE THIS PROGRAM FOR A CLASS, SO IF THIS IS NOT EXACTLY WHAT YOU ARE LOOKING FOR, KINDLY DISREGARD THIS POST.
Try this code-
#include <stdio.h>
#include<stdlib.h>
#include<string.h>
float reversDigits(float num)
{
char buffer[20],ch,*ptr;
int i,j,len;
snprintf(buffer,20,"%.3lf",num);
len = strlen(buffer);
for(i=0,j=len-1;i<j;i++,j--)
{
ch=buffer[i];
buffer[i]=buffer[j];
buffer[j]=ch;
}
buffer[len] = '\0';
return atof(buffer);
}
int main()
{
float num = 45000.062;
printf("Reverse of no. is %.5lf\n", reversDigits(num));
return 0;
}
Am passing a number with 3 digits after ., so i am using %.3lf in snprintf, if you simply use %lf means, while converting it to string it will add zeros and some numbers. To avoid that am using, else you need to do a little bit of more work to remove it!
Note: while converting string to float else float to string, in decimal position it will add some extra number or zero. The programmer need to take care of it!
I am doing a factorial program with strings because i need the factorial of Numbers greater than 250
I intent with:
string factorial(int n){
string fact="1";
for(int i=2; i<=n; i++){
b=atoi(fact)*n;
}
}
But the problem is that atoi not works. How can i convert my string in a integer.
And The most important Do I want to know if the program of this way will work with the factorial of 400 for example?
Not sure why you are trying to use string. Probably to save some space by not using integer vector? This is my solution by using integer vector to store factorial and print.Works well with 400 or any large number for that matter!
//Factorial of a big number
#include<iostream>
#include<vector>
using namespace std;
int main(){
int num;
cout<<"Enter the number :";
cin>>num;
vector<int> res;
res.push_back(1);
int carry=0;
for(int i=2;i<=num;i++){
for(int j=0;j<res.size();j++){
int tmp=res[j]*i;
res[j]=(tmp+carry)%10 ;
carry=(tmp+carry)/10;
}
while(carry!=0){
res.push_back(carry%10);
carry=carry/10;
}
}
for(int i=res.size()-1;i>=0;i--) cout<<res[i];
cout<<endl;
return 0;
}
Enter the number :400
Factorial of 400 :64034522846623895262347970319503005850702583026002959458684445942802397169186831436278478647463264676294350575035856810848298162883517435228961988646802997937341654150838162426461942352307046244325015114448670890662773914918117331955996440709549671345290477020322434911210797593280795101545372667251627877890009349763765710326350331533965349868386831339352024373788157786791506311858702618270169819740062983025308591298346162272304558339520759611505302236086810433297255194852674432232438669948422404232599805551610635942376961399231917134063858996537970147827206606320217379472010321356624613809077942304597360699567595836096158715129913822286578579549361617654480453222007825818400848436415591229454275384803558374518022675900061399560145595206127211192918105032491008000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
There's a web site that will calculate factorials for you: http://www.nitrxgen.net/factorialcalc.php. It reports:
The resulting factorial of 250! is 493 digits long.
The result also contains 62 trailing zeroes (which constitutes to 12.58% of the whole number)
3232856260909107732320814552024368470994843717673780666747942427112823747555111209488817915371028199450928507353189432926730931712808990822791030279071281921676527240189264733218041186261006832925365133678939089569935713530175040513178760077247933065402339006164825552248819436572586057399222641254832982204849137721776650641276858807153128978777672951913990844377478702589172973255150283241787320658188482062478582659808848825548800000000000000000000000000000000000000000000000000000000000000
Many systems using C++ double only work up to 1E+308 or thereabouts; the value of 250! is too large to store in such numbers.
Consequently, you'll need to use some sort of multi-precision arithmetic library, either of your own devising using C++ string values, or using some other widely-used multi-precision library (GNU GMP for example).
The code below uses unsigned double long to calculate very large digits.
#include<iostream.h>
int main()
{
long k=1;
while(k!=0)
{
cout<<"\nLarge Factorial Calculator\n\n";
cout<<"Enter a number be calculated:";
cin>>k;
if (k<=33)
{
unsigned double long fact=1;
fact=1;
for(int b=k;b>=1;b--)
{
fact=fact*b;
}
cout<<"\nThe factorial of "<<k<<" is "<<fact<<"\n";
}
else
{
int numArr[10000];
int total,rem=0,count;
register int i;
//int i;
for(i=0;i<10000;i++)
numArr[i]=0;
numArr[10000]=1;
for(count=2;count<=k;count++)
{
while(i>0)
{
total=numArr[i]*count+rem;
rem=0;
if(total>9)
{
numArr[i]=total%10;
rem=total/10;
}
else
{
numArr[i]=total;
}
i--;
}
rem=0;
total=0;
i=10000;
}
cout<<"The factorial of "<<k<<" is \n\n";
for(i=0;i<10000;i++)
{
if(numArr[i]!=0 || count==1)
{
cout<<numArr[i];
count=1;
}
}
cout<<endl;
}
cout<<"\n\n";
}//while
return 0;
}
Output:
![Large Factorial Calculator
Enter a number be calculated:250
The factorial of 250 is
32328562609091077323208145520243684709948437176737806667479424271128237475551112
09488817915371028199450928507353189432926730931712808990822791030279071281921676
52724018926473321804118626100683292536513367893908956993571353017504051317876007
72479330654023390061648255522488194365725860573992226412548329822048491377217766
50641276858807153128978777672951913990844377478702589172973255150283241787320658
18848206247858265980884882554880000000000000000000000000000000000000000000000000
000000000000][1]
You can make atoi compile by adding c_str(), but it will be a long way to go till getting factorial. Currently you have no b around. And if you had, you still multiply int by int. So even if you eventually convert that to string before return, your range is still limited. Until you start to actually do multiplication with ASCII or use a bignum library there's no point to have string around.
Your factorial depends on conversion to int, which will overflow pretty fast, so you want be able to compute large factorials that way. To properly implement computation on big numbers you need to implement logic as for computation on paper, rules that you were tought in primary school, but treat long long ints as "atoms", not individual digits. And don't do it on strings, it would be painfully slow and full of nasty conversions
If you are going to solve factorial for numbers larger than around 12, you need a different approach than using atoi, since that just gives you a 32-bit integer, and no matter what you do, you are not going to get more than 2 billion (give or take) out of that. Even if you double the size of the number, you'll only get to about 20 or 21.
It's not that hard (relatively speaking) to write a string multiplication routine that takes a small(ish) number and multiplies each digit and ripples the results through to the the number (start from the back of the number, and fill it up).
Here's my obfuscated code - it is intentionally written such that you can't just take it and hand in as school homework, but it appears to work (matches the number in Jonathan Leffler's answer), and works up to (at least) 20000! [subject to enough memory].
std::string operator*(const std::string &s, int x)
{
int l = (int)s.length();
std::string r;
r.resize(l);
std::fill(r.begin(), r.end(), '0');
int b = 0;
int e = ~b;
const int c = 10;
for(int i = l+e; i != e;)
{
int d = (s[i]-0x30) * x, p = i + b;
while (d && p > e)
{
int t = r[p] - 0x30 + (d % c);
r[p] = (t % c) + 0x30;
d = t / c + d / c;
p--;
}
while (d)
{
r = static_cast<char>((d % c) +0x30)+r;
d /= c;
b++;
}
i--;
}
return r;
}
In C++, the largest integer type is 'long long', and it hold 64 bits of memory, so obviously you can't store 250! in an integer type. It is a clever idea to use strings, but what you are basically doing with your code is (I have never used the atoi() function, so I don't know if it even works with strings larger than 1 character, but it doesn't matter):
covert the string to integer (a string that if this code worked well, in one moment contains the value of 249!)
multiply the value of the string
So, after you are done multiplying, you don't even convert the integer back to string. And even if you did that, at one moment when you convert the string back to an integer, your program will crash, because the integer won't be able to hold the value of the string.
My suggestion is, to use some class for big integers. Unfortunately, there isn't one available in C++, so you'll have to code it by yourself or find one on the internet. But, don't worry, even if you code it by yourself, if you think a little, you'll see it's not that hard. You can even use your idea with the strings, which, even tough is not the best approach, for this problem, will still yield the results in the desired time not using too much memory.
This is a typical high precision problem.
You can use an array of unsigned long long instead of string.
like this:
struct node
{
unsigned long long digit[100000];
}
It should be faster than string.
But You still can use string unless you are urgent.
It may take you a few days to calculate 10000!.
I like use string because it is easy to write.
#include <bits/stdc++.h>
#pragma GCC optimize (2)
using namespace std;
const int MAXN = 90;
int n, m;
int a[MAXN];
string base[MAXN], f[MAXN][MAXN];
string sum, ans;
template <typename _T>
void Swap(_T &a, _T &b)
{
_T temp;
temp = a;
a = b;
b = temp;
}
string operator + (string s1, string s2)
{
string ret;
int digit, up = 0;
int len1 = s1.length(), len2 = s2.length();
if (len1 < len2) Swap(s1, s2), Swap(len1, len2);
while(len2 < len1) s2 = '0' + s2, len2++;
for (int i = len1 - 1; i >= 0; i--)
{
digit = s1[i] + s2[i] - '0' - '0' + up; up = 0;
if (digit >= 10) up = digit / 10, digit %= 10;
ret = char(digit + '0') + ret;
}
if (up) ret = char(up + '0') + ret;
return ret;
}
string operator * (string str, int p)
{
string ret = "0", f; int digit, mul;
int len = str.length();
for (int i = len - 1; i >= 0; i--)
{
f = "";
digit = str[i] - '0';
mul = p * digit;
while(mul)
{
digit = mul % 10 , mul /= 10;
f = char(digit + '0') + f;
}
for (int j = 1; j < len - i; j++) f = f + '0';
ret = ret + f;
}
return ret;
}
int main()
{
freopen("factorial.out", "w", stdout);
string ans = "1";
for (int i = 1; i <= 5000; i++)
{
ans = ans * i;
cout << i << "! = " << ans << endl;
}
return 0;
}
Actually, I know where the problem raised At the point where we multiply , there is the actual problem ,when numbers get multiplied and get bigger and bigger.
this code is tested and is giving the correct result.
#include <bits/stdc++.h>
using namespace std;
#define mod 72057594037927936 // 2^56 (17 digits)
// #define mod 18446744073709551616 // 2^64 (20 digits) Not supported
long long int prod_uint64(long long int x, long long int y)
{
return x * y % mod;
}
int main()
{
long long int n=14, s = 1;
while (n != 1)
{
s = prod_uint64(s , n) ;
n--;
}
}
Expexted output for 14! = 87178291200
The logic should be:
unsigned int factorial(int n)
{
unsigned int b=1;
for(int i=2; i<=n; i++){
b=b*n;
}
return b;
}
However b may get overflowed. So you may use a bigger integral type.
Or you can use float type which is inaccurate but can hold much bigger numbers.
But it seems none of the built-in types are big enough.
How do I detect the length of an integer? In case I had le: int test(234567545);
How do I know how long the int is? Like telling me there is 9 numbers inside it???
*I have tried:**
char buffer_length[100];
// assign directly to a string.
sprintf(buffer_length, "%d\n", 234567545);
string sf = buffer_length;
cout <<sf.length()-1 << endl;
But there must be a simpler way of doing it or more clean...
How about division:
int length = 1;
int x = 234567545;
while ( x /= 10 )
length++;
or use the log10 method from <math.h>.
Note that log10 returns a double, so you'll have to adjust the result.
Make a function :
int count_numbers ( int num) {
int count =0;
while (num !=0) {
count++;
num/=10;
}
return count;
}
Nobody seems to have mentioned converting it to a string, and then getting the length. Not the most performant, but it definitely does it in one line of code :)
int num = -123456;
int len = to_string(abs(num)).length();
cout << "LENGTH of " << num << " is " << len << endl;
// prints "LENGTH of 123456 is 6"
You can use stringstream for this as shown below
stringstream ss;
int i = 234567545;
ss << i;
cout << ss.str().size() << endl;
if "i" is the integer, then
int len ;
char buf[33] ;
itoa (i, buf, 10) ; // or maybe 16 if you want base-16 ?
len = strlen(buf) ;
if(i < 0)
len-- ; // maybe if you don't want to include "-" in length ?
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int main() {
int i=2384995;
char buf[100];
itoa(i, buf, 10); // 10 is the base decimal
printf("Lenght: %d\n", strlen(buf));
return 0;
}
Beware that itoa is not a standard function, even if it is supported by many compilers.
len=1+floor(log10(n));//c++ code lib (cmath)
looking across the internet it's common to make the mistake of initializing the counter variable to 0 and then entering a pre-condition loop testing for as long as the count does not equal 0. a do-while loop is perfect to avoid this.
unsigned udc(unsigned u) //unsigned digit count
{
unsigned c = 0;
do
++c;
while ((u /= 10) != 0);
return c;
}
it's probably cheaper to test whether u is less than 10 to avoid the uneccessary division, increment, and cmp instructions for cases where u < 10.
but while on that subject, optimization, you could simply test u against constant powers of ten.
unsigned udc(unsigned u) //unsigned digit count
{
if (u < 10) return 1;
if (u < 100) return 2;
if (u < 1000) return 3;
//...
return 0; //number was not supported
}
which saves you 3 instructions per digit, but is less adaptable for different radixes inaddition to being not as attractive, and tedious to write by hand, in which case you'd rather write a routine to write the routine before inserting it into your program. because C only supports very finite numbers, 64bit,32bit,16bit,8bit, you could simply limit yourself to the maximum when generating the routine to benefit all sizes.
to account for negative numbers, you'd simply negate u if u < 0 before counting the number of digits. of course first making the routine support signed numbers.
if you know that u < 1000,
it's probably easier to just write, instead of writing the routine.
if (u > 99) len = 3;
else
if (u > 9) len = 2;
else len = 1;
Here are a few different C++ implementations* of a function named digits() which takes a size_t as argument and returns its number of digits. If your number is negative, you are going to have to pass its absolute value to the function in order for it to work properly:
The While Loop
int digits(size_t i)
{
int count = 1;
while (i /= 10) {
count++;
}
return count;
}
The Exhaustive Optimization Technique
int digits(size_t i) {
if (i > 9999999999999999999ull) return 20;
if (i > 999999999999999999ull) return 19;
if (i > 99999999999999999ull) return 18;
if (i > 9999999999999999ull) return 17;
if (i > 999999999999999ull) return 16;
if (i > 99999999999999ull) return 15;
if (i > 9999999999999ull) return 14;
if (i > 999999999999ull) return 13;
if (i > 99999999999ull) return 12;
if (i > 9999999999ull) return 11;
if (i > 999999999ull) return 10;
if (i > 99999999ull) return 9;
if (i > 9999999ull) return 8;
if (i > 999999ull) return 7;
if (i > 99999ull) return 6;
if (i > 9999ull) return 5;
if (i > 999ull) return 4;
if (i > 99ull) return 3;
if (i > 9ull) return 2;
return 1;
}
The Recursive Way
int digits(size_t i) { return i < 10 ? 1 : 1 + digits(i / 10); }
Using snprintf() as a Character Counter
⚠ Requires #include <stdio.h> and may incur a significant performance penalty compared to other solutions. This method capitalizes on the fact that snprintf() counts the characters it discards when the buffer is full. Therefore, with the right arguments and format specifiers, we can force snprintf() to give us the number of digits of any size_t.
int digits(size_t i) { return snprintf (NULL, 0, "%llu", i); }
The Logarithmic Way
⚠ Requires #include <cmath> and is unreliable for unsigned integers with more than 14 digits.
// WARNING! There is a silent implicit conversion precision loss that happens
// when we pass a large int to log10() which expects a double as argument.
int digits(size_t i) { return !i? 1 : 1 + log10(i); }
Driver Program
You can use this program to test any function that takes a size_t as argument and returns its number of digits. Just replace the definition of the function digits() in the following code:
#include <iostream>
#include <stdio.h>
#include <cmath>
using std::cout;
// REPLACE this function definition with the one you want to test.
int digits(size_t i)
{
int count = 1;
while (i /= 10) {
count++;
}
return count;
}
// driver code
int main ()
{
const int max = digits(-1ull);
size_t i = 0;
int d;
do {
d = digits(i);
cout << i << " has " << d << " digits." << '\n';
i = d < max ? (!i ? 9 : 10 * i - 1) : -1;
cout << i << " has " << digits(i) << " digits." << '\n';
} while (++i);
}
* Everything was tested on a Windows 10 (64-bit) machine using GCC 12.2.0 in Visual Studio Code .
As long as you are mixing C stdio and C++ iostream, you can use the snprintf NULL 0 trick to get the number of digits in the integer representation of the number. Specifically, per man 3 printf If the string exceeds the size parameter provided and is truncated snprintf() will return
... the number of characters (excluding the terminating null byte)
which would have been written to the final string if enough space
had been available.
This allows snprintf() to be called with the str parameter NULL and the size parameter 0, e.g.
int ndigits = snprintf (NULL, 0, "%d", 234567545)
In your case where you simply wish to output the number of digits required for the representation, you can simply output the return, e.g.
#include <iostream>
#include <cstdio>
int main() {
std::cout << "234567545 is " << snprintf (NULL, 0, "%d", 234567545) <<
" characters\n";
}
Example Use/Output
$ ./bin/snprintf_trick
234567545 is 9 characters
note: the downside to using the snprintf() trick is that you must provide the conversion specifier which will limit the number of digits representable. E.g "%d" will limit to int values while "%lld" would allow space for long long values. The C++ approach using std::stringstream while still limited to numeric conversion using the << operator handles the different integer types without manually specifying the conversion. Something to consider.
second note: you shouldn't dangle the "\n" of the end of your sprintf() conversion. Add the new line as part of your output and you don't have to subtract 1 from the length...
All I really know is PHP and I used the decbin function etc, It was fairly easy to do. In this C++ program I want to do the same thing, just a simple number or string how would I do this?
A simple function could be defined such as this:
void binary(int decimal) {
int remainder;
if(decimal <= 1) {
std::cout << decimal;
return;
}
remainder = decimal % 2;
binary(decimal >> 1);
std::cout << remainder;
}
Although there are many other resources on the web on how to do this..
A noteworthy question for efficiency of it here, as you may want more than just that:
Efficiently convert between Hex, Binary, and Decimal in C/C++
you can do this non-recursively using something like this:
std::string Dec2Bin(int nValue, bool bReverse = false)
{
std::string sBin;
while(nValue != 0)
{
sBin += (nValue & 1) ? '1' : '0';
nValue >>= 1;
}
if(!bReverse)
std::reverse(sBin.begin(),sBin.end());
return sBin;
}
of course this isn't too architucture friendly, but it avoids cout, just incase your not using a console. it also outputs in any bit ordering.
You can use itoa if it's available on your compiler. Just remember it's not standard and if you need a standard method you're better off using the other solutions posted.
If you want to print it, just use this code here. If you want to return a string, instead of using cout, append to a C++ string instead.
offering the iterative approach (pardon the #defines (but i'm quite sure they will be compiled to the expression's value), i don't quite remember predefined macro/constants in C):
#define INT_ARCH 32
#define ARCH_SHIFTABLE (INT_ARCH - 1)
#define ARCH_MAX_INT 1 << ARCH_SHIFTABLE
void dec_to_bin(int decimal)
{
int shifter = ARCH_MAX_INT;
for(; shifter > 0; shifter >>= 1)
cout << (decimal & shifter);
}
Similar to #Necrolis answer without the need for an if, and the reversal of the string.
string decimalToBinary(int decimal) {
string binary;
while(decimal) {
binary.insert(0, 1, (decimal & 1) + '0');
decimal >>= 1;
}
return binary;
}
Do with simple way in c++
#include <iostream>
using namespace std;
int main()
{
long n, rem, binary=0, i=1;
cout<<"Enter a int: ";
cin>>n;
while(n != 0)
{
rem = n%2;
n = n/2;
binary= binary + (rem*i);
i = i*10;
}
cout<< "\nAns: "<<binary <<endl;
return 0;
}