#include <iostream>
using namespace std;
// node defined
class node {
public:
int data;
node *link;
node(int d) {
data = d;
link = NULL;
}
};
// printing the linked list
void print(node *head) {
node *current = head;
while (current != NULL) {
cout << current->data << " ";
current = current->link;
}
cout << endl;
}
// creating the linked list with 'n' nodes
node *createlist(int n) {
node *head = NULL;
node *t = NULL;
for (int i = 0; i < n; i++) {
node *temp = NULL;
int num;
cin >> num;
temp = new node(num);
if (head == NULL) {
head = temp;
t = temp;
continue;
}
if (t->link == NULL)
t->link = temp;
t = temp;
}
return head;
}
// performing selection sort on the linked list in an iterative manner
void my_selection_sort_linked_list(node *&head) {
node *min = head; // throughout the algorithm 'min' is used to denote the
// node with min value out of all the nodes left for
// scanning while scanning if we find a node 'X' with
// value lesser than min, then we update the pointers in
// such a way that 'X' becomes the predecessor of 'min'
node *current =
min->link; // 'current' refers to the current node we are scanning
node *previous = min; //'previous' refers to the node that is previous to
// the current node
node *temp =
NULL; // 'temp' in this algo is used to point to the last node of the
// sorted part of the linked list.
// eg. If at any time instance the state of the linked list is
// suppose 1->2->5->3->8->NULL then, we see that "1->2" is the
// sorted part of the LL, and therefore temp will be pointing to
// the last node of the sorted part,i.e,'2' We keep on arranging
// the Linked list in such a way that after each iteration the
// node with 'min' value is placed at its correct position. Eg.
// Let suppose initially we have 5->4->1->3->2->NULL After 1st
// iteration : 1->4->5->3->2->NULL and so on
while (
min->link !=
NULL) // so that all the nodes are scanned or until there exists a node
{
// pick the first node from the unsorted part and assume that it is the
// minimum and then start scanning from the next node
while (current != NULL) // suppose you choose the min node to be X,
// then scan starts from the (X+1)th node until
// its NULL. current = (X+1)th node and min = X
{
if (current->data < min->data) // if the current node is smaller
// than the presumed node 'min'
{
if (temp == NULL) // temp stays null for the first iteration,
// therefore it symbolizes that we are
// scanning for the first time
{
if (previous ==
min) // if the 'previous' is pointing to the 'min' node
{
// Update the pointers
head = current; // update the head pointer with the
// current node
min->link = current->link;
current->link = previous;
min = current;
current = previous->link;
} else // if the 'previous' is not pointing to the 'min'
// node
{
// Update the pointers
head = current; // update the head pointer with the
// current node
previous->link = current->link;
current->link = min;
min = current;
current = previous->link;
}
} else // if 'temp' is not NULL, i.e., its not the 1st
// iteration
{
temp->link = current;
previous->link = current->link;
current->link = min;
min = current;
current = previous->link;
}
} else // if the current node is greater than min, just move the
// previous and the current pointer a step further
{
previous = previous->link;
current = current->link;
}
}
// update the pointers. Set 'temp' to the last node in the sorted part.
// Make 'min' move a step further so that 'min' points to the 1st node
// of the unsorted part start the iteration again
temp = min;
min = min->link;
previous = min;
current = min->link;
}
}
// Test cases:
// enter the no. of nodes : 5
// 8 9 3 1 4
// original list is : 8 9 3 1 4
// sorted list is : 1 3 4 8 9
// enter the no. of nodes : 3
// -1 -2 -3
// original list is : -1 -2 -3
// sorted list is : -3 -2 -1
// enter the no. of nodes : 8
// 8 7 6 5 4 3 2 1
// original list is : 8 7 6 5 4 3 2 1
// sorted list is : 1 2 3 4 5 6 7 8
// enter the no. of nodes : 6
// 5 3 4 1 -2 -4
// original list is : 5 3 4 1 -2 -4
// sorted list is : -4 -2 1 3 4 5
int main() {
node *head = NULL;
int n;
cout << "enter the no. of nodes : "; // taking input from user about the
// number of nodes in linked list
cin >> n;
if (n == 0)
return 0;
head = createlist(n); // creating the list
cout << "original list is : ";
print(head); // printing the original linked list
my_selection_sort_linked_list(head); // applying selection sort
cout << "sorted list is : ";
print(head); // printing the sorted linked list
return 0;
}