How do I convert my char array that reads 50 characters to a string array that reads an unlimited amount of charaters

[ApacheOmega]

I'm trying to change my char array to string so an unlimited amount of characters can be entered instead of it being a limit ex. (char DNA[50]) this means I can only enter 50 DNA characters but I want it to be unlimited. The idea i had is to change the char DNA[50] to string DNA; then declaring int DNA length and then DNAlength=DNA.Length(). well I enter that in my code and I have problems here's my original code

#include<iostream>
#include<fstream>
#include <string>
using namespace std;
void KeyInput()
{

char DNA[50];
char RNA[50];

cout<<"Enter DNA Sequence"<<endl;
int len=0;
cin>>DNA;
for(int i=0; i<=sizeof(DNA); i++){

if (DNA[i] == 'A')
{cout<<"U";
RNA[i]='U';
len++;
}
if (DNA[i] == 'G')
{cout<<"C";
RNA[i]='C';
len++;
}
if (DNA[i] == 'C')
{cout<<"G";
RNA[i]='G';
len++;
}

if (DNA[i] == 'T')
{cout<<"A";
RNA[i]='A';
len++;
}

}
cout<<endl;
for(int i=0; i<len; i++){
cout<<RNA[i];
}
cout<<endl<<sizeof(DNA)<<endl;
cout<<len<<endl;
fstream file;
file.open("IOResults.txt",ios::out);
file<<DNA<<endl<<RNA<<endl;
file.close();

}

How do I change this to read and store an Unlimited amount of characters????
do I even have to change my char to string to do this?

[sigmablack]

google before you ask a question,
all you need to do is dynamically allocate the size
this way

int size=500;//any size you want
char * buffer;//pointer
buffer = new char [size];// 

[coder777]

Use string instead of the array:

http://www.cplusplus.com/reference/string/string/

[ne555]

The idea i had is to change the char DNA[50] to string DNA; then declaring int DNA length and then DNAlength=DNA.Length(). well I enter that in my code and I have problems here's my original code

http://www.cplusplus.com/forum/articles/40071/#msg216313
_ Don't post code which is different from your own but does not reproduce the problem ( or has other problems )
http://www.cplusplus.com/forum/articles/40071/#msg218019
_ Be specific about why it doesn't work.

[JLBorges]

void KeyInput()
{
    std::string DNA ;
    std::cout << " Enter DNA Sequence: " ;
    std::cin >> DNA ;

    std::string RNA ;
    for( std::size_t i = 0 ; i < DNA.size() ; ++i )
    {
        switch( DNA[i] )
        {
            case 'A' : RNA += 'U' ; break ;
            case 'G' : RNA += 'C' ; break ;
            case 'C' : RNA += 'G' ; break ;
            case 'T' : RNA += 'A' ; break ;
            default : std::cerr << "error in input " << DNA[i] << '\n' ;
        }
    }

    std::ofstream file ( "IOResults.txt" ) ;
    file << DNA << '\n' << RNA << '\n';
}

[vlad from moscow]

An alternative code.

std::string::size_type KeyInput()
{
    const size_t N = 5;
    const DUMMY_CHAR = '?';
    const char DNA_CHAR[N] = "AGCT";
    const char RNA_CHAR[N] = "UCGA";
   
    std::string DNA ;
    std::cout << " Enter DNA Sequence: " ;
    std::cin >> DNA ;

    std::string RNA ;
    RNA.reserve( DNA.size() );

    for ( std::string::value_type c : DNA  )
    {
        char *p = std::strchr( DNA_CHAR, c );

        if ( p ) 
        {
            RNA += RNA_CHAR[p - DNA_CHAR];
        }
        else 
        {
            std::cerr << "error in input " << DNA[i] << '\n' ;
            RNA += DUMMY_CHAR;
        }
    }

    std::ofstream file ( "IOResults.txt" ) ;
    file << DNA << '\n' << RNA << '\n';

    return ( DNA.size() );
}

[ApacheOmega]

Thanks alot fellas
you guys make me realize I got a whole lot to learn
how long does it usually take to get to a pretty confident level of being a legit programmer?
6 months? 1 year?
whats the average time i should expect to become good at this?

[sigmablack]

there always room for improvement, but i think within a month or two you should be able to do most of the basic things in a good way :)