ALT This approach reverses a singly linked list by changing the direction of each node's next pointer. Three pointers are used: prev to store the previous node, temp as the current node, and front to store the next node before modifying links. The list is traversed once, and during each iteration the current node's link is reversed. After all nodes are processed, prev points to the new head of the reversed linked list. Time Complexity: O(N) Space Complexity: O(1)
ALT This approach finds the middle node of a linked list using two traversals. In the first traversal, the total number of nodes is counted. Using the count, the middle position is calculated. In the second traversal, the list is traversed again until the middle position is reached, and that node is returned. For an even-length list, the second middle node is returned. Time Complexity: O(N) Space Complexity: O(1)
ALT This approach merges two sorted linked lists into a single sorted linked list. A dummy node is used to simplify the merging process. The current nodes of both lists are compared, and the smaller node is attached to the merged list. This process continues until one list becomes empty. The remaining nodes of the other list are then attached directly to the merged list. Finally, the merged list starting from dummy.next is returned. Time Complexity: O(N M) Space Complexity: O(1)
