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Copy constructor for very simple singly linked list?
I am having quite a bit of difficulty understanding how to implement a copy constructor for a singly linked list. Heres is the code I have for the implementation:
-------------------------------------------------------
struct node {
string value;
node * next;
};
class strSet {
private:
node * first;
public:
...
strSet (const strSet& copy);
...
};
------------------------------------------------------
I am having difficulty implementing this copy constructor. Can anyone shed some light? I'm not sure what to put in the body.
strSet (const strSet& copy) {
if( copy->first == NULL) first = NULL;
.....
The other public member functions don't relate to the copy constructor. I'm suppose to do a deep copy manually.
2 Answers
- sheldonlinkerLv 61 decade ago
First, let's do this one step at a time:
strSet(const strSet ©) {
...first = copy.first; // Copy the pointer to their node, for a starter
...struct node **next = &first; // Show that we're working on the First pointer
...while (**next) { // Proceed while we need to clone nodes
......struct node *newNode = malloc(sizeof(struct node); // Allocate a node
......*newNode = **next; // Fill it
......*next = newNode; // Have the pointer we're working on point at the new storage
......next = &newNode->next; // Advance to work on the next pointer
...}
}
This collapses to:
strSet(const strSet ©) {
...first = copy.first;
...for (struct node **next=&first; **next; next=&newNode->next) {
......struct node *newNode = malloc(sizeof(struct node);
......*newNode = **next;
......*next = newNode;
...}
}
