for_each for Node manually c++ - c++

Question

How can I implement for_each for that implementation of Node and List?
I'm sure it's not long code, can some share a few strokes of his knowledge please? Do I need to implement it as template or just as inner function.
Thanks for helping.
class Node {
int data;
Node *next;
public:
Node() {}
void SetData(int aData) { data = aData; }
void SetNext(Node *aNext) {
next = aNext;
}
int Data() { return data; }
Node* Next() { return next; }
};
// List class
class List {
Node *head;
public:
List() { head = nullptr; }
void Append(int data){
// Create a new node
Node *newNode = new Node();
newNode->SetData(data);
newNode->SetNext(nullptr);
// Create a temp pointer
Node *tmp = head;
if ( tmp != nullptr ) {
// Nodes already present in the list
// Parse to end of list
while ( tmp->Next() != nullptr) {
tmp = tmp->Next();
}
// Point the last node to the new node
tmp->SetNext(newNode);
}
else {
// First node in the list
head = newNode;
}
}
void Delete(int data){
// Create a temp pointer
Node *tmp = head;
// No nodes
if ( tmp == nullptr ) return;
// Last node of the list
if ( tmp->Next() == nullptr ) {
delete tmp;
head = nullptr;
}
else {
// Parse thru the nodes
Node* prev;
do {
if ( tmp->Data() == data ) break;
prev = tmp;
tmp = tmp->Next();
} while ( tmp != nullptr );
// Adjust the pointers
if (tmp->Next()!=nullptr) prev->SetNext(tmp->Next());
else prev->SetNext(nullptr);
// Delete the current node
if (tmp!=nullptr) delete tmp;
}
}
};
EDIT:
This is use of iterator:
for (List<Pair, CompareFunction>::myIterator it = this->_pairs.begin();
it != this->_pairs.end(); ++it) {
Pair cur_pair = *it;
if (cur_pair.first == key) {
this->_pairs.Delete(cur_pair);
this->_size--;
}
}
This is Pair Class as sub-class in another template class:
template <class KeyType, class ValueType, class CompareFunction = std::less<KeyType> >
class MtmMap {
public:
class Pair {
public:
Pair():first(KeyType()){} ////////////////////
Pair(const KeyType& key, const ValueType& value)
: first(key), second(value) {}
const KeyType first;
ValueType second;
~Pair() = default;
In our concrete case KeyType and ValueType run as both int.

Answer 1

Add the following code into your List class:
class List{
...
class myIterator
{
public:
typedef myIterator self_type;
typedef Node* pointer;
myIterator(pointer ptr) : ptr_(ptr) { }
self_type operator++() {
self_type i = *this;
if (ptr_) ptr_ = ptr_->Next();
return i;
}
int operator*() { if (ptr_ ) return ptr_->Data(); else return 0; }
bool operator==(const self_type& rhs) {
if (!ptr_ && !rhs.ptr_) return true;
return (ptr_ && rhs.ptr_ && rhs.ptr_->Data()==ptr_->Data());
}
bool operator!=(const self_type& rhs) {
return !(*this==rhs);
}
private:
pointer ptr_ = nullptr;
};
myIterator begin() { return myIterator(head); }
myIterator end() { return myIterator(nullptr); }
};
You may then use normal iterators like in the following example:
List l;
l.Append(2);
l.Append(5);
l.Append(7);
l.Append(11);
for (int i: l) std::cout << i << std::endl;
//or
for (myIterator it=l.begin(); it!=l.end(); ++it) std::cout << *it << std::endl;