convert vector of char to an int - c++

I need to convert a part of vectors of chars to an int.
If I have
std::vector<char> // which contains something like asdf1234dsdsd
and I want to take characters from the 4th till 7th position and convert it into an int.
The positions are always known.
How do I do it the fastest way ?
I tried to use global copy and got a weird answer. Instead of 2 I got 48.

If the positions are known, you can do it like this
int x = (c[4] - '0') * 1000 + (c[5] - '0') * 100 + (c[6] - '0') * 10 + c[7] - '0';

This is fairly flexible, although it doesn't check for overflow or anything fancy like that:
#include <algorithm>
int base10_digits(int a, char b) {
return 10 * a + (b - '0');
}
int result = std::accumulate(myvec.begin()+4, myvec.begin()+8, 0, base10_digits);

The reason copying didn't work is probably because of endianness, assuming the first char is the most significant:
int x = (int(c[4]) << 24) + (int(c[5]) << 16) + (int(c[6]) << 8) + c[7]

1.Take the address of the begin and end (one past the end) index.
2.Construct a std::string from it.
3.Feed it into a std::istringstream.
4.Extract the integer from the stringstream into a variable.
(This may be a bad idea!)

Try this:
#include <iostream>
#include <vector>
#include <math.h>
using namespace std;
int vtoi(vector<char> vec, int beg, int end) // vector to int
{
int ret = 0;
int mult = pow(10 , (end-beg));
for(int i = beg; i <= end; i++) {
ret += (vec[i] - '0') * mult;
mult /= 10;
}
return ret;
}
#define pb push_back
int main() {
vector<char> vec;
vec.pb('1');
vec.pb('0');
vec.pb('3');
vec.pb('4');
cout << vtoi(vec, 0, 3) << "\n";
return 0;
}

long res = 0;
for(int i=0; i<vec.size(); i++)
{
res += vec[i] * pow (2, 8*(vec.size() - i - 1)); // 8 means number of bits in byte
}

Related

Formatting Commas into a long long integer

this is my first time posting a question. I was hoping to get some help on a very old computer science assignment that I never got around to finishing. I'm no longer taking the class, just want to see how to solve this.
Read in an integer (any valid 64-bit
integer = long long type) and output the same number but with commas inserted.
If the user entered -1234567890, your program should output -1,234,567,890. Commas
should appear after every three significant digits (provided more digits remain) starting
from the decimal point and working left toward more significant digits. If the number
entered does not require commas, do not add any. For example, if the input is 234 you
should output 234. The input 0 should produce output 0. Note in the example above
that the number can be positive or negative. Your output must maintain the case of the
input.
I'm relatively new to programming, and this was all I could come up with:
#include <iostream>
#include <cmath>
using namespace std;
int main()
{
long long n;
cout << "Enter an integer:" << endl;
cin >> n;
int ones = n % 10;
int tens = n / 10 % 10;
int hund = n / 100 % 10;
int thous = n / 1000 % 10;
int tthous = n / 10000 % 10;
cout << tthous << thous << "," << hund << tens << ones << endl;
return 0;
}
The original assignment prohibited the use of strings, arrays, and vectors, so please refrain from giving suggestions/solutions that involve these.
I'm aware that some sort of for-loop would probably be required to properly insert the commas in the necessary places, but I just do not know how to go about implementing this.
Thank you in advance to anyone who offers their help!
Just to give you an idea how to solve this, I've maiden a simple implementation. Just keep in mind that is just a simple example:
#include <iostream>
#include <cmath>
using namespace std;
int main()
{
long long n = -1234567890;
if ( n < 0 )
cout << '-';
n = abs(n);
for (long long i = 1000000000000; i > 0; i /= 1000) {
if ( n / i <= 0 ) continue;
cout << n / i ;
n = n - ( n / i) * i;
if ( n > 0 )
cout << ',';
}
return 0;
}
http://coliru.stacked-crooked.com/a/150f75db89c46e99
The easy solution would be to use ios::imbue to set a locale that would do all the work for you:
std::cout.imbue(std::locale(""));
std::cout << n << std::endl;
However, if the restraints don't allow for strings or vectors I doubt that this would be a valid solution. Instead you could use recursion:
void print(long long n, int counter) {
if (n > 0) {
print(n / 10, ++counter);
if (counter % 3 == 0) {
std::cout << ",";
}
std::cout << n%10;
}
}
void print(long long n) {
if (n < 0) {
std::cout << "-";
n *= -1;
}
print(n, 0);
}
And then in the main simply call print(n);
A small template class comma_sep may be a solution, the usage may be as simple as:
cout << comma_sep<long long>(7497592752850).sep() << endl;
Which outputs:
7,497,592,752,850
Picked from here:
https://github.com/arloan/libimsux/blob/main/comma_sep.hxx
template <class I = int, int maxdigits = 32>
class comma_sep
char buff[maxdigits + maxdigits / 3 + 2];
char * p;
I i;
char sc;
public:
comma_sep(I i, char c = ',') : p(buff), i(i), sc(c) {
if (i < 0) {
buff[0] = '-';
*++p = '\0';
}
}
const char * sep() {
return _sep(std::abs(i));
}
private:
const char * _sep(I i) {
I r = i % 1000;
I n = i / 1000;
if (n > 0) {
_sep(n);
p += sprintf(p, "%c%03d", sc, (int)r);
*p = '\0';
} else {
p += sprintf(p, "%d", (int)r);
*p = '\0';
}
return buff;
}
};
The above class handles only integeral numbers, float/double numbers need to use a partial specialized version:
template<int maxd>
class comma_sep<double, maxd> {
comma_sep<int64_t, maxd> _cs;
char fs[64];
double f;
public:
const int max_frac = 12;
comma_sep(double d, char c = ',') : _cs((int64_t)d, c) {
double np;
f = std::abs(modf(d, &np));
}
const char * sep(int frac = 3) {
if (frac < 1 || frac > max_frac) {
throw std::invalid_argument("factional part too too long or invalid");
}
auto p = _cs.sep();
strcpy(fs, p);
char fmt[8], tmp[max_frac+3];
sprintf(fmt, "%%.%dlf", frac);
sprintf(tmp, fmt, f);
return strcat(fs, tmp + 1);
}
};
The two above classes can be improved by adding type-traits like std::is_integral and/or std::is_floating_point, though.

Dividing pointer char array to other arrays

When I printed it I got error like this 17:1733╠╠╠╠╠╠╠╠17:╠╠.
I couldn't figure it out. I would appreciate if you solve and give me a better approach? Thanks for your help.
#include "stdafx.h"
#include <iostream>
#include <conio.h>
#include <cstdlib>
#include <iomanip>
#include <string>
using namespace std;
int main()
{
char* time = "173324";
char holdh[3];
char holdM[3];
char holds[3];
holdh[2] = '\0';
holdM[2] = '\0';
holds[2] = '\0';
int t;
for (t = 0; t < 6;t++)
{
if (t < 2)
holdh[t] = *(time + t);
else if (2 <= t < 4) {
t = t - 2;
holdM[t] = *(time + t);
t = t + 2;
}
else if (4 <= t < 6)
{
t = t - 4;
holds[t] = *(time + t);
t = t + 4;
}
}
string h(holdh);
string M(holdM);
string s(holds);
string datex = h + ":" + M + ":" + s;
cout << datex;
return 0;
}
It might be overflow of memory but I tried to prevent that by assigning null values. So if I have a problem in there too please inform. Thanks again.
The expression 2 <= t < 4 is equal to (2 <= t) < 4. That is, check if the result of 2 <= t (which is a bool true or false) is smaller than 4, which is will always be as boolean results are either 0 (for false) or 1 (for true).
If you want to compare a range, you need to to e.g. 2 <= t && t < 4.
More generally, I advice you to not use a loop for this. Do the assignments directly instead:
// Create three arrays and initialize all elements to zero
char holdh[3] = {};
char holdM[3] = {};
char holds[3] = {};
holdh[0] = time[0];
holdh[1] = time[1];
holdM[0] = time[2];
holdM[1] = time[3];
holds[0] = time[4];
holds[1] = time[5];
Much simpler and show your intent much more clearly.
And you don't even need the temporary holdX variables, as you can just get the sub-strings from time and initialize h, M and s directly:
const char* time = "173324";
std::string h(time + 0, time + 2);
std::string M(time + 2, time + 4);
std::string s(time + 4, time + 6);
And do you really need the also temporary h, M and s variables?
std::cout << std::string(time + 0, time + 2) << ':'
<< std::string(time + 2, time + 4) << ':'
<< std::string(time + 4, time + 6) << '\n';
And do you really need freshly allocated strings?
std::cout << std::string_view(time + 0, 2) << ':'
<< std::string_view(time + 2, 2) << ':'
<< std::string_view(time + 4, 2) << '\n';
Your code is an textbook example of bad use of if() statement inside of loop.
What happens that you repeat all same checks in every iterations, while you actually know where iterations must stop.
And you made assumption that if() checks every comparison inside its expression. It doesn't. It evaluates expression and checks if result is equivalent of non-zero value or boolean true. Thus if(4 <= t < 6) is a bug. It's an equivalent of if( (4 <= t) < 6 ). (a <= t) < b is always true, if b is grater than 1.
SImplest conversion of your code would be:
#include <iostream>
#include <cstdlib>
#include <iomanip>
#include <string>
using std::string;
using std::cout;
int main()
{
const char* time = "173324";
// note, that making it non-const is a not standard compliant
char hold[3][3] = {}; // zero initialization
for (int t = 0; t < 6;t++)
{
hold[t / 2][t % 2] = time[t];
}
string h(hold[0]);
string M(hold[1]);
string s(hold[2]);
string datex = h + ":" + M + ":" + s;
cout << datex;
return 0;
}
Or maybe even so:
string hold[3];
for (int t = 0; t < 6;t++)
{
hold[t / 2] += time[t];
}
string datex = hold[0] + ":" + hold[1] + ":" + hold[2];
But better you should avoid making loops at all, provided string got constructor that receives iterators for beginning and end of source.
std::string h(time + 0, time + 2);

Karatsuba Integer Multiplication failing with segmentation fault

As I run the program, it crashes with segmentation fault. Also, when I debug the code in codeblocks IDE, I am unable to debug it as well. The program crashes even before debugging begins. I am not able to understand the problem. Any help would be appreciated. Thanks!!
#include <iostream>
#include <math.h>
#include <string>
using namespace std;
// Method to make strings of equal length
int makeEqualLength(string& fnum,string& snum){
int l1 = fnum.length();
int l2 = snum.length();
if(l1>l2){
int d = l1-l2;
while(d>0){
snum = '0' + snum;
d--;
}
return l1;
}
else if(l2>l1){
int d = l2-l1;
while(d>0){
fnum = '0' + fnum;
d--;
}
return l2;
}
else
return l1;
}
int singleDigitMultiplication(string& fnum,string& snum){
return ((fnum[0] -'0')*(snum[0] -'0'));
}
string addStrings(string& s1,string& s2){
int length = makeEqualLength(s1,s2);
int carry = 0;
string result;
for(int i=length-1;i>=0;i--){
int fd = s1[i]-'0';
int sd = s2[i]-'0';
int sum = (fd+sd+carry)%10+'0';
carry = (fd+sd+carry)/10;
result = (char)sum + result;
}
result = (char)carry + result;
return result;
}
long int multiplyByKaratsubaMethod(string fnum,string snum){
int length = makeEqualLength(fnum,snum);
if(length==0) return 0;
if(length==1) return singleDigitMultiplication(fnum,snum);
int fh = length/2;
int sh = length - fh;
string Xl = fnum.substr(0,fh);
string Xr = fnum.substr(fh,sh);
string Yl = snum.substr(0,fh);
string Yr = snum.substr(fh,sh);
long int P1 = multiplyByKaratsubaMethod(Xl,Yl);
long int P3 = multiplyByKaratsubaMethod(Xr,Yr);
long int P2 = multiplyByKaratsubaMethod(addStrings(Xl,Xr),addStrings(Yl,Yr)) - P1-P3;
return (P1*pow(10,length) + P2*pow(10,length/2) + P3);
}
int main()
{
string firstNum = "62";
string secondNum = "465";
long int result = multiplyByKaratsubaMethod(firstNum,secondNum);
cout << result << endl;
return 0;
}
There are three serious issues in your code:
result = (char)carry + result; does not work.The carry has a value between 0 (0 * 0) and 8 (9 * 9). It has to be converted to the corresponding ASCII value:result = (char)(carry + '0') + result;.
This leads to the next issue: The carry is even inserted if it is 0. There is an if statement missing:if (carry/* != 0*/) result = (char)(carry + '0') + result;.
After fixing the first two issues and testing again, the stack overflow still occurs. So, I compared your algorithm with another I found by google:Divide and Conquer | Set 4 (Karatsuba algorithm for fast multiplication)(and possibly was your origin because it's looking very similar). Without digging deeper, I fixed what looked like a simple transfer mistake:return P1 * pow(10, 2 * sh) + P2 * pow(10, sh) + P3;(I replaced length by 2 * sh and length/2 by sh like I saw it in the googled code.) This became obvious for me seeing in the debugger that length can have odd values so that sh and length/2 are distinct values.
Afterwards, your program became working.
I changed the main() function to test it a little bit harder:
#include <cmath>
#include <iostream>
#include <string>
using namespace std;
string intToStr(int i)
{
string text;
do {
text.insert(0, 1, i % 10 + '0');
i /= 10;
} while (i);
return text;
}
// Method to make strings of equal length
int makeEqualLength(string &fnum, string &snum)
{
int l1 = (int)fnum.length();
int l2 = (int)snum.length();
return l1 < l2
? (fnum.insert(0, l2 - l1, '0'), l2)
: (snum.insert(0, l1 - l2, '0'), l1);
}
int singleDigitMultiplication(const string& fnum, const string& snum)
{
return ((fnum[0] - '0') * (snum[0] - '0'));
}
string addStrings(string& s1, string& s2)
{
int length = makeEqualLength(s1, s2);
int carry = 0;
string result;
for (int i = length - 1; i >= 0; --i) {
int fd = s1[i] - '0';
int sd = s2[i] - '0';
int sum = (fd + sd + carry) % 10 + '0';
carry = (fd + sd + carry) / 10;
result.insert(0, 1, (char)sum);
}
if (carry) result.insert(0, 1, (char)(carry + '0'));
return result;
}
long int multiplyByKaratsubaMethod(string fnum, string snum)
{
int length = makeEqualLength(fnum, snum);
if (length == 0) return 0;
if (length == 1) return singleDigitMultiplication(fnum, snum);
int fh = length / 2;
int sh = length - fh;
string Xl = fnum.substr(0, fh);
string Xr = fnum.substr(fh, sh);
string Yl = snum.substr(0, fh);
string Yr = snum.substr(fh, sh);
long int P1 = multiplyByKaratsubaMethod(Xl, Yl);
long int P3 = multiplyByKaratsubaMethod(Xr, Yr);
long int P2
= multiplyByKaratsubaMethod(addStrings(Xl, Xr), addStrings(Yl, Yr))
- P1 - P3;
return P1 * pow(10, 2 * sh) + P2 * pow(10, sh) + P3;
}
int main()
{
int nErrors = 0;
for (int i = 0; i < 1000; i += 3) {
for (int j = 0; j < 1000; j += 3) {
long int result
= multiplyByKaratsubaMethod(intToStr(i), intToStr(j));
bool ok = result == i * j;
cout << i << " * " << j << " = " << result
<< (ok ? " OK." : " ERROR!") << endl;
nErrors += !ok;
}
}
cout << nErrors << " error(s)." << endl;
return 0;
}
Notes about changes I've made:
Concerning std library: Please, don't mix headers with ".h" and without. Every header of std library is available in "non-suffix-flavor". (The header with ".h" are either C header or old-fashioned.) Headers of C library have been adapted to C++. They have the old name with prefix "c" and without suffix ".h".
Thus, I replaced #include <math.h> by #include <cmath>.
I couldn't resist to make makeEqualLength() a little bit shorter.
Please, note, that a lot of methods in std use std::size_t instead of int or unsigned. std::size_t has appropriate width to do array subscript and pointer arithmetic i.e it has "machine word width". I believed a long time that int and unsigned should have "machine word width" also and didn't care about size_t. When we changed in Visual Studio from x86 (32 bits) to x64 (64 bits), I learnt the hard way that I had been very wrong: std::size_t is 64 bits now but int and unsigned are still 32 bits. (MS VC++ is not an exception. Other compiler vendors (but not all) do it the same way.)I inserted some C type casts to remove the warnings from compiler output. Such casts to remove warnings (regardless you use C casts or better the C++ casts) should always be used with care and should be understood as confirmation: Dear compiler. I see you have concerns but I (believe to) know and assure you that it should work fine.
I'm not sure about your intention to use long int in some places. (Probably, you transferred this code from original source without caring about.) As your surely know, the actual size of all int types may differ to match best performance of the target platform. I'm working on a Intel-PC with Windows 10, using Visual Studio. sizeof (int) == sizeof (long int) (32 bits). This is independent whether I compile x86 code (32 bits) or x64 code (64 bits). The same is true for gcc (on cygwin in my case) as well as on any Intel-PC with Linux (AFAIK). For a granted larger type than int you have to choose long long int.
I did the sample session in cygwin on Windows 10 (64 bit):
$ g++ -std=c++11 -o karatsuba karatsuba.cc
$ ./karatsuba
0 * 0 = 0 OK.
0 * 3 = 0 OK.
0 * 6 = 0 OK.
etc. etc.
999 * 993 = 992007 OK.
999 * 996 = 995004 OK.
999 * 999 = 998001 OK.
0 error(s).
$

Converting an array of 2 digit numbers into an integer (C++)

Is it possible to take an array filled with 2 digit numbers e.g.
[10,11,12,13,...]
and multiply each element in the list by 100^(position in the array) and sum the result so that:
mysteryFunction[10,11,12] //The function performs 10*100^0 + 11*100^1 + 12*100^3
= 121110
and also
mysteryFunction[10,11,12,13]
= 13121110
when I do not know the number of elements in the array?
(yes, the reverse of order is intended but not 100% necessary, and just in case you missed it the first time the numbers will always be 2 digits)
Just for a bit of background to the problem: this is to try to improve my attempt at an RSA encryption program, at the moment I am multiplying each member of the array by 100^(the position of the number) written out each time which means that each word which I use to encrypt must be a certain length.
For example to encrypt "ab" I have converted it to an array [10,11] but need to convert it to 1110 before I can put it through the RSA algorithm. I would need to adjust my code for if I then wanted to use a three letter word, again for a four letter word etc. which I'm sure you will agree is not ideal. My code is nothing like industry standard but I am happy to upload it should anyone want to see it (I have also already managed this in Haskell if anyone would like to see that). I thought that the background information was necessary just so that I don't get hundreds of downvotes from people thinking that I'm trying to trick them into doing homework for me. Thank you very much for any help, I really do appreciate it!
EDIT: Thank you for all of the answers! They perfectly answer the question that I asked but I am having problems incorporating them into my current program, if I post my code so far would you be able to help? When I tried to include the answer provided I got an error message (I can't vote up because I don't have enough reputation, sorry that I haven't accepted any answers yet).
#include <iostream>
#include <string>
#include <math.h>
int returnVal (char x)
{
return (int) x;
}
unsigned long long modExp(unsigned long long b, unsigned long long e, unsigned long long m)
{
unsigned long long remainder;
int x = 1;
while (e != 0)
{
remainder = e % 2;
e= e/2;
if (remainder == 1)
x = (x * b) % m;
b= (b * b) % m;
}
return x;
}
int main()
{
unsigned long long p = 80001;
unsigned long long q = 70021;
int e = 7;
unsigned long long n = p * q;
std::string foo = "ab";
for (int i = 0; i < foo.length(); i++);
{
std::cout << modExp (returnVal((foo[0]) - 87) + returnVal (foo[1] -87) * 100, e, n);
}
}
If you want to use plain C-style arrays, you will have to separately know the number of entries. With this approach, your mysterious function might be defined like this:
unsigned mysteryFunction(unsigned numbers[], size_t n)
{
unsigned result = 0;
unsigned factor = 1;
for (size_t i = 0; i < n; ++i)
{
result += factor * numbers[i];
factor *= 100;
}
return result;
}
You can test this code with the following:
#include <iostream>
int main()
{
unsigned ar[] = {10, 11, 12, 13};
std::cout << mysteryFunction(ar, 4) << "\n";
return 0;
}
On the other hand, if you want to utilize the STL's vector class, you won't separately need the size. The code itself won't need too many changes.
Also note that the built-in integer types cannot handle very large numbers, so you might want to look into an arbitrary precision number library, like GMP.
EDIT: Here's a version of the function which accepts a std::string and uses the characters' ASCII values minus 87 as the numbers:
unsigned mysteryFunction(const std::string& input)
{
unsigned result = 0;
unsigned factor = 1;
for (size_t i = 0; i < input.size(); ++i)
{
result += factor * (input[i] - 87);
factor *= 100;
}
return result;
}
The test code becomes:
#include <iostream>
#include <string>
int main()
{
std::string myString = "abcde";
std::cout << mysteryFunction(myString) << "\n";
return 0;
}
The program prints: 1413121110
As benedek mentioned, here's an implementation using dynamic arrays via std::vector.
unsigned mystery(std::vector<unsigned> vect)
{
unsigned result = 0;
unsigned factor = 1;
for (auto& item : vect)
{
result += factor * item;
factor *= 100;
}
return result;
}
void main(void)
{
std::vector<unsigned> ar;
ar.push_back(10);
ar.push_back(11);
ar.push_back(12);
ar.push_back(13);
std::cout << mystery(ar);
}
I would like to suggest the following solutions.
You could use standard algorithm std::accumulate declared in header <numeric>
For example
#include <iostream>
#include <numeric>
int main()
{
unsigned int a[] = { 10, 11, 12, 13 };
unsigned long long i = 1;
unsigned long long s =
std::accumulate( std::begin( a ), std::end( a ), 0ull,
[&]( unsigned long long acc, unsigned int x )
{
return ( acc += x * i, i *= 100, acc );
} );
std::cout << "s = " << s << std::endl;
return 0;
}
The output is
s = 13121110
The same can be done with using the range based for statement
#include <iostream>
#include <numeric>
int main()
{
unsigned int a[] = { 10, 11, 12, 13 };
unsigned long long i = 1;
unsigned long long s = 0;
for ( unsigned int x : a )
{
s += x * i; i *= 100;
}
std::cout << "s = " << s << std::endl;
return 0;
}
You could also write a separate function
unsigned long long mysteryFunction( const unsigned int a[], size_t n )
{
unsigned long long s = 0;
unsigned long long i = 1;
for ( size_t k = 0; k < n; k++ )
{
s += a[k] * i; i *= 100;
}
return s;
}
Also think about using std::string instead of integral numbers to keep an encrypted result.

C++ bit string to int conversion

I am trying to convert a bit string (bitString) of length 'sLength' to an int.
The following code works fine for me in my computer. Is there any case where it may not work?
int toInt(string bitString, int sLength){
int tempInt;
int num=0;
for(int i=0; i<sLength; i++){
tempInt=bitString[i]-'0';
num=num+tempInt * pow(2,(sLength-1-i));
}
return num;
}
Thanks in advance
pow works with doubles. Result may be inaccurate. Use bit arithmetic instead
num |= (1 << (sLength-1-i)) * tempInt;
Don't also forget about cases when bitString contains symbols other than '0' and '1' or too long
Or, you can let the standard library do the heavy lifting:
#include <bitset>
#include <string>
#include <sstream>
#include <climits>
// note the result is always unsigned
unsigned long toInt(std::string const &s) {
static const std::size_t MaxSize = CHAR_BIT*sizeof(unsigned long);
if (s.size() > MaxSize) return 0; // handle error or just truncate?
std::bitset<MaxSize> bits;
std::istringstream is(s);
is >> bits;
return bits.to_ulong();
}
Why not change your for loop to the more efficient and far more simple C++11 version:
for (char c : bitString)
num = (num << 1) | // Shift the current set of bits to the left one bit
(c - '0'); // Add in the current bit via a bitwise-or
By the way, you should also check that the number of bits specified does not overrun an int and you may want to make sure that each char in the string is either a '0' or '1'.
Answer and notice about inaccuracy of floating-point numbers already given; here's a more readable implementation with integer arithmetic, though:
int toInt(const std::string &s)
{
int n = 0;
for (int i = 0; i < s.size(); i++) {
n <<= 1;
n |= s[i] - '0';
}
return n;
}
Notes:
You don't need an explicit length. That's why we have std::string::length().
Counting from zero results in cleaner code, because you don't have to do the subtraction every time.
for (std::string::reverse_iterator it = bitString.rbegin();
it != bitString.rend(); ++it) {
num *= 2;
num += *it == '1' ? 1 : 0;
}
I see directly three cases where it may not work :
pow Works with double, your result may be inaccurate, you can fix it with :
num |= tempInt * ( 1 << ( sLength - 1 - i ) );
If bitString[i] is not a '0' or '1',
If your number in the string in bigger than the int limit.
If you have control over the last two points, your resulting code could be :
int toInt( const string& bitString )
{
int num = 0;
for ( char c : bitString )
{
num <<= 1;
num |= ( c - '0' );
}
return num;
}
Don't forget the const reference as a parameter.