C Exercises: Reorder even-numbered before odd in a singly linked list

C Singly Linked List : Exercise-30 with Solution

Write a C program to create and reorder a linked list placing all even-numbered nodes ahead of all odd-numbered nodes.

Sample Solution:

C Code:

#include<stdio.h>
#include <stdlib.h>

struct Node {
    int data;
    struct Node* next;
};

// Function to create a new node
struct Node* newNode(int data) {
    struct Node* node = (struct Node*) malloc(sizeof(struct Node));
    node->data = data;
    node->next = NULL;
    return node;
}

struct Node* odd_Even_List(struct Node* head) {
  if (!head) return head;
  struct Node *odd = head, *even = head->next, *even_Head = even;
  while (even && even->next) {
    odd->next = even->next;
    odd = odd->next;
    even->next = odd->next;
    even = even->next;
  }
  odd->next = even_Head;
  return head;
}


// Function to print a linked list
void displayList(struct Node* head) {
    while (head) {
        printf("%d ", head->data);
        head = head->next;
    }
    printf("\n");
}

int main() {
	struct Node* head = newNode(1);
    head->next = newNode(2);
    head->next->next = newNode(3);
    head->next->next->next = newNode(4);
    head->next->next->next->next = newNode(5);
    head->next->next->next->next->next = newNode(6);
    printf("Original Singly List:\n");
	displayList(head);
	struct Node* result;
	result = odd_Even_List(head);
	printf("\nReorder the said linked list placing all even-numbered \nnodes ahead of all odd-numbered nodes:\n");
	displayList(result);
    return 0;
}

Sample Output:

Original Singly List:
1 2 3 4 5 6 

Reorder the said linked list placing all even-numbered 
nodes ahead of all odd-numbered nodes:
1 3 5 2 4 6 

Flowchart :

C Programming Code Editor:

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