Write a program to concatenate two strings in C plus plus?

Answer 1

#include
#include

using std::cin;
using std::cout;
using std::endl;
using std::string;
using std::getline;

int main()
{
string firstLine = "";
cout << endl << "Enter first line: ";
getline(cin, firstLine);

string secondLine = "";
cout << endl << "Enter second line: ";
getline(cin, secondLine);

cout << endl << "Two strings concatenated together: " << firstLine + secondLine << endl;

system("PAUSE");
return 0;
}

Answer 2

There is no need to create a class to do this since std::string already caters for string manipulations. However, the following stripped down implementation demonstrates how std::string implements concatenations using an embedded std::vector template of type char in a new class named str. Note that this is the C++ way of doing things -- there is no need to maintain a dynamic array of char, nor any need to use malloc/calloc, realloc and free (all of which are C-style concepts, not C++ concepts). All that functionality is encapsulated by the std::vector template, which is itself embedded in std::string (and its std::wstring counterpart).

#include<iostream>

#include<vector>

class str

{

public:

~str(){}

str(){m_data.push_back(0);}

str(const str& rhs):m_data(rhs.m_data){}

str(const char* rhs);

str operator+(str& rhs);

str& operator+=(str& rhs);

const char* c_str(){return(&m_data[0]);}

private:

std::vector<char> m_data;

};

// overloaded constructor (rhs must be NULL-terminated!):

str::str(const char* rhs)

{

char* p = (char*)rhs;

do

m_data.push_back(*p);

while(*p++);

}

// addition operator overload (concatenate)

str str::operator+ (str& rhs)

{

str s(*this);

s+=rhs;

return(s);

}

// compound addition operator overload (append)

str& str::operator+= (str& rhs)

{

m_data.pop_back();

std::vector<char>::iterator it=rhs.m_data.begin();

while(it!=rhs.m_data.end())

m_data.push_back(*it++);

return(*this);

}

// Demonstration of usage:

int main()

{

str s1 = "Hello ";

str s2 = "world!";

str s3 = s1 + s2;

std::cout<<s3.c_str()<<std::endl;

return(0);

}

Output:

Hello world!