#include <iostream>
// Node structure for singly linked list
struct Node {
int data; // value stored in the node
Node* next; // pointer to the next node
Node(int val) : data(val), next(nullptr) {}
};
// Reverse the linked list in-place
Node* reverseList(Node* head) {
Node* prev = nullptr; // will become the new head
Node* current = head; // pointer to traverse the list
Node* next = nullptr; // temporary pointer to store next node
while (current != nullptr) {
next = current->next; // save next node
current->next = prev; // reverse the link
prev = current; // move prev forward
current = next; // move current forward
}
return prev; // prev is the new head after full reversal
}
// Print the linked list
void printList(Node* head) {
Node* temp = head;
while (temp != nullptr) {
std::cout << temp->data;
if (temp->next != nullptr) std::cout << " -> ";
temp = temp->next;
}
std::cout << std::endl;
}
int main() {
// Create a sample list: 1 -> 2 -> 3 -> 4 -> 5
Node* head = new Node(1);
head->next = new Node(2);
head->next->next = new Node(3);
head->next->next->next = new Node(4);
head->next->next->next->next = new Node(5);
std::cout << "Original list:\n";
printList(head);
// Reverse the list
head = reverseList(head);
std::cout << "Reversed list:\n";
printList(head);
}
/*
run:
Original list:
1 -> 2 -> 3 -> 4 -> 5
Reversed list:
5 -> 4 -> 3 -> 2 -> 1
*/
