Output not as expected from the array - c++

Question

I am writing a code where I take user user text input, convert it to binary, store each binary character in an element in an array and then print A or T for 0 and G or C for 1 at random. But the ATGC seem to not follow this rule and they come at random for every digit; 0 and 1. So If the binary is 0010101 I need output as ATGACTG. Also when I store the binary in an int variable, the zero in front of it vanishes. Is there a way to keep it?
#include <iostream>
#include <cstdlib>
#include <bitset>
#include <string>
#include <ctime>
int main()
{
using namespace std;
int p, i=0, a[100000];
int s;
string myString;
int binary;
cout << "Type your text: ";
std::getline (std::cin,myString);
for (std::size_t k=0; k < myString.size(); ++k)
{
std::bitset<8> y(myString[k]);
std::string dna = y.to_string();
binary = atoi(dna.c_str());
cout << binary;
while (binary != 0)
{
a[i] = binary % 10;
binary = binary / 10;
i++;
}
}
std::cout << std::endl;
srand(time(0));
for (int j = (i-1); j>-1; j--)
{
if (a[j] == 0)
{
p = rand() %2;
if (p==0)
cout<< "A";
else
cout<< "T";
}
if (a[j] == 1)
{
s = rand() %2;
if (s == 0)
cout<< "G";
else
cout<< "C";
}
else
{
cout << "";
}
}
}

Answer 1

I don't know why exactly you wrote so much wrong code, but I've managed to extract (and change) the code that actually does the job.
#include <iostream>
#include <string>
#include <bitset>
#include <ctime>
int main()
{
int i = 0, a[8];
std::string myString;
std::cout << "Type your text: " << std::endl;
std::getline(std::cin, myString);
for(auto x : std::bitset<8>(myString).to_string())
a[i++] = x == '1';
std::cout << std::endl;
srand(time(0));
for(int j = 0; j < i; ++j)
if(a[j] == 0)
std::cout << (rand() % 2 ? "T" : "A");
else if(a[j] == 1)
std::cout << (rand() % 2 ? "C" : "G");
std::cout << std::endl;
}
And here's neater version of main:
int main()
{
std::vector<int> a; // using std::vector
std::bitset<8> bs;
std::cout << "Type your text: " << std::endl;
std::cin >> bs; // std::bitset can be read from stream via operator>>
for(auto x : bs.to_string())
a.push_back(x == '1');
std::cout << std::endl;
srand(time(0));
for(auto x : a)
if(x == 0)
std::cout << (rand() % 2 ? "T" : "A");
else if(x == 1)
std::cout << (rand() % 2 ? "C" : "G");
std::cout << std::endl;
}
Just ask if you want an explanation on some specific part.

Answer 2

I told you not to convert the string to an integer. You didn't listen. This is why leading 0 vanishes.
Your output seams to be completely random because you reverse the order of characters in the sequence when reading the information from a.
Here is how I'd solve your problem: run online
#include <iostream>
#include <string>
#include <bitset>
#include <ctime>
#include <cstdlib>
int main()
{
std::cout << "Type your text: " << std::endl;
std::string in_str;
std::getline(std::cin, in_str);
std::string binary_str;
for(int i = 0; i < in_str.size(); ++i)
{
char c = in_str.at(i);
binary_str.append(std::bitset<8>(c).to_string());
}
std::cout << binary_str << std::endl;
srand(time(0));
for(int i = 0; i < binary_str.size(); ++i)
{
char c = binary_str.at(i);
if(c == '0')
std::cout << (rand() % 2 ? "T" : "A");
else
std::cout << (rand() % 2 ? "C" : "G");
}
std::cout << std::endl;
}
If you have any questions, ask me in the comments.
Edit: the OP asked me to explain all mistakes in his program.
Where did all those zeros gone?
To answer this question I'll have to explain all things your program does line-by-line.
Here you convert a symbol to a bitset:
std::bitset<8> y(myString[k])
For example: if k is 'a', then the y would be 01100001.
Here you convert the bitset to a string:
std::string dna = y.to_string();
In our example the dna would be "01100001".
Here you convert the string to an integer:
binary = atoi(dna.c_str());
A very simplified version of what atoi does:
binary = 0;
for(int i = 0; i < dna.size(); ++i)
binary = binary * 10 + (dna.at(i) - '0')
In our example the binary would be 1100001.
Note: that's NOT where you loose zeros. At this point you are still able to extract them because you know that you need to extract 8 digits. So you can append leading zeros to up it's length to 8.
The next line is where you actually loose zeros the first time because cout doesn't know that you want to print 8 digits.
cout << binary;
In our example it would print 1100001.
And here you loose zeros again because you stop extracting digits as soon as binary == 0 even if you extracted less than 8 digits. Also note that you are actually reversing what the function atoi just did with the only difference that you don't get your leading zeros back and the reverse order of bits (see the next paragraph):
while (binary != 0)
{
a[i] = binary % 10;
binary = binary / 10;
i++;
}
Why the output is "random"?
Here you are iterating through myString in the standard order
for (std::size_t k=0; k < myString.size(); ++k)
e.g. if myString is "abc" than
in the first iteration myString[k] would be 'a'
in the second iteration myString[k] would be 'b'
in the third iteration myString[k] would be 'c':
But in this loop you extract digits in reverse order:
while (binary != 0)
{
a[i] = binary % 10;
binary = binary / 10;
i++;
}
eg if binary is 1100001
in the 1st iteration you extract 1 and binary becomes 110000
in the 2nd iteration you extract 0 and binary becomes 11000
in the 3rd iteration you extract 0 and binary becomes 1100
in the 4th iteration you extract 0 and binary becomes 110
in the 5th iteration you extract 0 and binary becomes 11
in the 6th iteration you extract 1 and binary becomes 1
in the 7th iteration you extract 1 and binary becomes 0
Now you end up with an array where bits inside a character code are reversed, but different characters are stored in the array in the normal order.
e.g. If the input string was "abc", then a would become:
1,0,0,0,0,1,1, 0,1,0,0,0,1,1, 1,1,0,0,0,1,1
reversed 'a' reversed 'b' reversed 'c'
If you iterate through a in normal order, the order of bits inside character codes would be reversed. If you iterate through a in reverse order, you get the reversed order of characters.
As a rule of thumb: don't program by guessing, program by thinking.
Further reading
The Zen of Python. Most of this aphorisms are applicable to every programming language with the exception of Brainfuck
Raw C arrays are evil