// Let X = (x1, x2….xn) and Y = (y1, y2….yn) be 2 linked lists. Assume that, in each list,
// the nodes are in non-decreasing order of the data field values. Write an algorithm to
// merge two lists to obtain a new linked list Z in which the nodes are also in the non-
// decreasing order. Following the merge, X and Y do not exist as individual lists. Each
// node initially in X or Y is now in Z. Do not use additional nodes.

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

typedef struct node *nodePtr;
struct node {
    int data;
    nodePtr link;
};

nodePtr merge(nodePtr x, nodePtr y)
{
    nodePtr z, temp;
    if (!x) return y;
    if (!y) return x;
    if (x->data <= y->data) {
        z = x;
        x = x->link;
    } else {
        z = y;
        y = y->link;
    }
    temp = z;
    while (x && y) {
        if (x->data <= y->data) {
            temp->link = x;
            x = x->link;
        } else {
            temp->link = y;
            y = y->link;
        }
        temp = temp->link;
    }
    if (x) temp->link = x;
    if (y) temp->link = y;
    return z;
}

void printList(nodePtr head)
{
    while (head) {
        printf("%d ", head->data);
        head = head->link;
    }
    printf("\n");
}

nodePtr createNode(int data)
{
    nodePtr newNode = (nodePtr)malloc(sizeof(struct node));
    newNode->data = data;
    newNode->link = NULL;
    return newNode;
}

int main()
{
    nodePtr x = createNode(1);
    x->link = createNode(3);
    x->link->link = createNode(5);

    nodePtr y = createNode(2);
    y->link = createNode(4);
    y->link->link = createNode(6);

    printf("List X: ");
    printList(x);
    printf("List Y: ");
    printList(y);

    nodePtr z = merge(x, y);

    printf("Merged list Z: ");
    printList(z);

    return 0;
}