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Find kth node from Middle towards Head of a Linked List in C++
In this problem, we are given a linked-list and a number k. Our task is to find kth node from Middle towards the Head of a Linked List.
Let’s take an example to understand the problem,
Input: linked-list : 4 -> 2 -> 7 -> 1 -> 9 -> 12 -> 8 -> 10 -> 5, k = 2
Output: 7
Explanation:
Middle node value is 9.
The 2nd node from middle towards head is 7.
Solution Approach
We need to find kth element from the middle of the linked-list towards the beginning. For this we need to find the size of linked-list by traversing the linked-list from beginning to end and find size.
K element from the middle towards the start is the (n/2 + 1 - k)th element from the beginning.
Program to illustrate the working of our solution,
Example
#include <iostream>
using namespace std;
struct Node {
int data;
struct Node* next;
};
void pushNode(struct Node** head_ref, int new_data)
{
struct Node* new_node = new Node;
new_node->data = new_data;
new_node->next = (*head_ref);
(*head_ref) = new_node;
}
int findKmiddleNode(struct Node* head_ref, int k) {
int n = 0;
struct Node* counter = head_ref;
while (counter != NULL) {
n++;
counter = counter->next;
}
int reqNode = ((n / 2 + 1) - k);
if (reqNode <= 0)
return -1;
struct Node* current = head_ref;
int count = 1;
while (current != NULL) {
if (count == reqNode)
return (current->data);
count++;
current = current->next;
}
}
int main()
{
struct Node* head = NULL;
int k = 2;
pushNode(&head, 5);
pushNode(&head, 10);
pushNode(&head, 8);
pushNode(&head, 12);
pushNode(&head, 9);
pushNode(&head, 1);
pushNode(&head, 7);
pushNode(&head, 2);
pushNode(&head, 4);
cout<<k<<"th element from beginning towards head is "<<findKmiddleNode(head, k);
return 0;
}Output
2th element from beginning towards head is 7
Updated on: 25-Jan-2021
307 Views
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