How do you write C plus plus string concat without builtin functions?

Answer 1

#include<iostream>

#include<string>

int main()

{

// the two strings to concatenate

std::string str1 = "Hello ";

std::string str2 = "world!";

// allocate memory to the concatenated string with null-terminator

char* str3 = new char[str1.size() + str2.size() + 1];

// initialise a moving pointer

char* p = str3;

// copy from the first string

memcpy( p, str1.c_str(), str1.size() );

// advance the pointer

p += str1.size();

// copy from the second string

memcpy( p, str2.c_str(), str2.size() );

// advance the pointer

p += str2.size();

// set the null-terminator

*p = 0;

// print concatenated string

std::cout << str3 << std::endl;

// tidy up

delete [] str3, str3 = NULL;

}