What is wrong with this copy constructor for a very basic singly linked list?

Without the copy constructor, my program works fine. I can declare as many empty or singleton strSets as I want and output their value without a problem in my main program. As soon as I put in the copy constructor, if I declare more than 2 sets, i get Segmentation Fault. Also, if I declare two sets and try to output the value of either, I get Segmentation Fault. If theres only one set declare it works fine. I'll need the copy constructor for when I implement the rest of my program obv, but if it doesnt work here, but it would work later on either. Heres the code:

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**Here is the implementation of the class strSet.h**

#ifndef _STRSET_

#define _STRSET_

#include <iostream>

#include <vector>

#include <string>

struct node {

std::string s1;

node * next;

};

class strSet {

private:

node * first;

public:

strSet (); // Create empty set

strSet (std::string s); // Create singleton set

strSet (const strSet ©); // Copy constructor

// will implement destructor and overloaded assignment operator later

void output() const;

}; // End of strSet class

#endif // _STRSET_

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**And heres the implementation strSet.cpp**

#include <iostream>

#include <vector>

#include <string>

#include "strset2.h"

using namespace std;

strSet::strSet() {

first = NULL;

}

strSet::strSet(string s) {

node *temp;

temp = new node;

temp->s1 = s;

temp->next = NULL;

first = temp;

}

strSet::strSet(const strSet& copy) {

cout << "copy-cst\n";

node *n = copy.first;

node *prev = NULL;

while (n) {

node *newNode = new node;

newNode->s1 = n->s1;

newNode->next = NULL;

if (prev) {

prev->next = newNode;

}

else {

first = newNode;

}

prev = newNode;

n = n->next;

}

}

void strSet::output() const {

if(first == NULL) {

cout << "Empty set\n";

}

else {

node *temp;

temp = first;

while(1) {

cout << temp->s1 << endl;

if(temp->next == NULL) break;

temp = temp->next;

}

}

}