Given a linked list, the task is to make a function which checks whether the length of the linked list is even or odd.
Examples:
Input : 1->2->3->4->NULL Output : Even Input : 1->2->3->4->5->NULL Output : Odd
Method 1: Count the codes linearly
Traverse the entire Linked List and keep counting the number of nodes. As soon as the loop is finished, we can check if the count is even or odd. You may try it yourself.
Method 2: Stepping 2 nodes at a time
Approach:
1. Take a pointer and move that pointer two nodes at a time 2. At the end, if the pointer is NULL then length is Even, else Odd.
C++
// C++ program to check length // of a given linklist #include <bits/stdc++.h>using namespace std; // Defining structure class Node { public: int data; Node* next; }; // Function to check the length // of linklist int LinkedListLength(Node* head) { while (head && head->next) { head = head->next->next; } if (!head) return 0; return 1; } // Push function void push(Node** head, int info) { // Allocating node Node* node = new Node(); // Info into node node->data = info; // Next of new node to head node->next = (*head); // head points to new node (*head) = node; } // Driver code int main(void) { Node* head = NULL; // Adding elements to Linked List push(&head, 4); push(&head, 5); push(&head, 7); push(&head, 2); push(&head, 9); push(&head, 6); push(&head, 1); push(&head, 2); push(&head, 0); push(&head, 5); push(&head, 5); int check = LinkedListLength(head); // Checking for length of // linklist if(check == 0) { cout << "Even"; } else { cout << "Odd"; } return 0; } // This is code is contributed by rathbhupendra |
Output:
Odd
Time Complexity: O(n)
Auxiliary Space: O(1)
Method: Using Recursion
C++
// C++ program to check length // of a given linklist #include <bits/stdc++.h>using namespace std; // Defining structure class Node { public: int data; Node* next; }; //Recursive Function to check the length // of linklist int LinkedListLength(Node* head) { if(head == NULL) { return 0; } return 1 + LinkedListLength(head->next); } // Push function void push(Node** head, int info) { // Allocating node Node* node = new Node(); // Info into node node->data = info; // Next of new node to head node->next = (*head); // head points to new node (*head) = node; } // Driver code int main(void) { Node* head = NULL; // Adding elements to Linked List push(&head, 4); push(&head, 5); push(&head, 7); push(&head, 2); push(&head, 9); push(&head, 6); push(&head, 1); push(&head, 2); push(&head, 0); push(&head, 5); push(&head, 5); int check = LinkedListLength(head); // Checking for length of // linklist if(check == 0) { cout << "Even"; } else { cout << "Odd"; } return 0; } // This is code is contributed by vinay pinjala. |
Output
Odd
Time Complexity: O(n)
Auxiliary Space: O(n)
Please refer complete article on Check whether the length of given linked list is Even or Odd for more details!
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