wrong output

[4w7X92yv]

Hello

I wrote a program that converts a binary value to a dec number
But it converts wrong:

input : 1111100
output:31

but 31 decimal is 0011111 binary
1111100 binary is 124 decimal

what do i do wrong?

#include <iostream>
#include <cstdlib>
#include <string>
#include <cmath>
using namespace std;
int main()
{
  string bin;
  double dec = 0;
  
  cin >> bin;
  
  for(int counter = 0; counter < bin.size(); counter++)
    if(bin.c_str()[counter] == '1')
      dec += pow(2.0, (double)counter);

  cout << dec << endl;
  
  system ("pause");
  return 0;
}

[LB]

Numbers in any base are read from right to left, so why do you read left to right?

[4w7X92yv]

If the user inputs 1111100 it outputs 31 while it should be 124
If the user inputs 0011111 it outputs 124 while that should be 31

Idk what i do wrong but its something

[Texan40]

#include <iostream>
#include <cstdlib>
#include <string>
#include <cmath>

using namespace std;

int main()
{
  string bin;
  // double dec = 0; // decimal or "floating point" number are in IEEE representation this won't work unless the binary string is the full 64 bits and appropriately constructed
  long long dec = 0; // could use char, short, int, etc depending on the size of the string entered

  cin >> bin;

  for(int counter = 0; counter < bin.size(); counter++)
    if(bin.at(counter) == '1') // don't know why you'd output a const cstring before taking the index? this is preferred.
    {
      dec += pow(2.0,double(bin.size() - 1 - counter)); // we're starting on the left-hand (most significant) side of the string
    }
  cout << dec << endl; // this will always be calculated as unsigned
  return 0;
}

[Texan40]

std::bitset already does this too:

#include <bitset>
#include <iostream>
#include <string>

int main()
{
  std::string bin;
  std::getline(std::cin,bin);
  std::bitset<64> bs_ulong(bin);
  std::cout << bs_ulong.to_ulong() << std::endl;
  return 0;
}

[4w7X92yv]

thanks :)