Question

Could anyone help me solve this problem in C++?

Write a function that sorts a linked list. (Use any sort algorithm, make sure to state which one your going to use.)

Answer 1

Solution : Using Merge Sort to sort a given linked list.

Code :

#include <bits/stdc++.h>
using namespace std;

class Node {
public:
int data;
Node* next;
};

/* utility functions */

Node* SortedList(Node* a, Node* b);

void Split(Node* source,Node** start, Node** end);

/* sorting the linked list by changing next pointers (not data) */
void mergeSort(Node** dummyHead)
{
Node* head = *dummyHead;
Node* a;
Node* b;

/* Base case -- length 0 or 1 */
if ((head == NULL) || (head->next == NULL)) {
return;
}

/* Split head into 'a' and 'b' sublists */
Split(head, &a, &b);

/* Recursively sorting the sublists */
mergeSort(&a);
mergeSort(&b);

/* merging the two sorted lists together */
*dummyHead = SortedList(a, b);
}

Node* SortedList(Node* a, Node* b)
{
Node* result = NULL;

/* Base case */
if (a == NULL)
return (b);
else if (b == NULL)
return (a);

if (a->data <= b->data) {
result = a;
result->next = SortedList(a->next, b);
}
else {
result = b;
result->next = SortedList(a, b->next);
}
return (result);
}

/* Splitting the nodes of the list into two halves i.e starting and ending and returning the lists using reference parameters. */
void Split(Node* source,Node** start, Node** end)
{
Node* fast;
Node* slow;
slow = source;
fast = source->next;

/* increment 'fast' two nodes, and advance 'slow' one node */
while (fast != NULL) {
fast = fast->next;
if (fast != NULL) {
slow = slow->next;
fast = fast->next;
}
}

/* if 'slow' is before the midpoint in the list, we split it in two
at that point. */
*start = source;
*end = slow->next;
slow->next = NULL;
}

/* printing nodes of the linked list*/
void printList(Node* node)
{
while (node != NULL) {
cout << node->data << " ";
node = node->next;
}
}

/* inserting node at the beginning of the linkedlist */
void push(Node** dummy_head, int new_data)
{
/* allocate node */
Node* new_node = new Node();

/* put in the data */
new_node->data = new_data;

/* link the old list off the new node */
new_node->next = (*dummy_head);

/* move the head to point to the new node */
(*dummy_head) = new_node;
}

int main()
{
/* Starting with an empty list */
Node* res = NULL;
Node* a = NULL;

/*pushing elements in the linked list*/
push(&a, 13);
push(&a, 8);
push(&a, 4);
push(&a, 18);
push(&a, 6);
push(&a, 1);

/* Sorting the linkedlist*/
mergeSort(&a);

cout << "Sorted Linked List : \n";
printList(a);

return 0;
}

#include bits/stdc++.h> using namespace std; Çclass Node { public: int data; Node* next; Ll: 4 4 /* utility functions / Node SortedList (Nodea, Node b); 4 4 4 void Split (Node source, Node** start, Node** end); 4 4 4 4 /* sorting the linked list by changing next pointers (not data) */ void merge Sort (Node** dummyHead) -11 Node head = dummyHead; Node* a; Node b; 4 1 1 1 1 1 / Base case -- length 0 or 1 */ if ((head == NULL) || (head->next == NULL)) { return; 1 1 1 1 /* Split head into an and a sublists / Split (head, sa, cb); 1 1 ASAAAASSSSSSSSSSSSSSS 1 1 /* Recursively sort the sublists / merge Sort (sa); merge Sort (sb); /* merging the two sorted lists together / dummyHead = SortedList(a, b); Node SortedList (Nodea, Node b) { Node result = NULL; /* Base case / if (a == NULL) return (b); else if (b == NULL) return (a); if (a->data (= b->data) { result = a; result->next = SortedList (a->next, b);

result = a; result->next = SortedList (a->next, b); else { result = b; result->next = SortedList(a, b->next); return (result); /* Splitting the nodes of the given list into starting and ending halves, and returning the two lists using the reference parameters./ void Split (Node* source, Node** start, Node** end) { Nodefast; Node slow; slow = source; fast = source->next; one node */ /* increment was two nodes, and advance wat while (fast != NULL) { fast = fast->next; if (fast != NULL) { slow = slow->next; fast = fast->next; /* if wat is before the midpoint in the list, we split it in two at that point. */ *start = source; *end = slow->next; slow->next = NULL; /* printing nodes of the linked list / void printList (Node node) while (node != NULL) { cout << node->data << " "; node = node->next; 7* inserting node at the beginning of the Junked void push (Node** dummy_head, int new_data) */ /allocate node */ Node* new_node = new Node(); 100 101 102 103 104 /put in the data / new node->data = new data;

new_node->data = new_data; /* link the old list off the new node */ new_node->next = ("durmy_head); /* move the head to point to the new node/ (*dummy_head) = new_node; 21 int main() { /* Starting with an empty list / Noderes = NULL; Node a = NULL; OOOOO O EEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEE aun W NO co o un WNO o coa in WNO coin w w w w w w WNNNNNNNNNN / pushing elements in the linked list / push(ca, 13); push(ça, 8); push(ça, 4); push(ca, 18); push(sa, 6); push(ça, 1); /* Sorting the w merge Sort (sa); hite cout << "Sorted Linked List : \n"; printList (a); return 0;

Output :

Sorted Linked List : 1 4 6 8 13 18 Process returned 0 (0x0_ Press any key to continue. execution time: 0.013 s