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reverseLinkedListIterAndRecurse.cpp
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reverseLinkedListIterAndRecurse.cpp
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#include <iostream>
struct Node {
int data;
Node * next;
Node( int d ) : data{ d }, next{ nullptr } { }
};
void push( Node * & head, int data ) {
Node *newNode = new Node(data);
if ( head == nullptr ) {
head = newNode;
} else {
Node *curr = head;
while( curr->next != nullptr ) {
curr = curr->next;
}
curr->next = newNode;
}
}
void printList( Node * head ) {
while( head ) {
std::cout << head->data << "-->";
head = head->next;
}
std::cout << "NULL" << std::endl;
}
void reverseIter( Node * & head ) {
//length of list is less than 2
if ( head == nullptr || ( head != nullptr && head->next == nullptr )) {
return;
}
Node *newHead = nullptr;
Node *curr = head;
Node *prev = nullptr;
while( curr != nullptr ) {
prev = curr;
curr = curr->next;
prev->next = newHead;
newHead = prev;
}
head = newHead;
}
void reverseRecur( Node * & head ) {
if ( head == nullptr || ( head != nullptr && head->next == nullptr ) ) {
return;
}
Node * first = head;
Node * rest = head->next;
reverseRecur( rest );
first->next->next = first;
first->next = nullptr;
head = rest;
}
int main() {
Node *head = nullptr;
push( head, 1 );
push( head, 2 );
push( head, 3 );
push( head, 4 );
push( head, 5 );
std::cout << "Before Reversing Linkedlist: ";
printList( head );
reverseIter( head );
std::cout << "After Reversing Linkedlist once: ";
printList( head );
reverseRecur( head );
std::cout << "After Reversing Linkedlist twice: ";
printList( head );
return 0;
}