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## Friday, 27 March 2015

### implementation of selection sorting algorithm in C

Implementation of selection sorting algorithm in C

/*
* implementation of selection sorting algorithm in C
*/

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

enum BOOL {FALSE, TRUE};
typedef int BOOL;

struct NODE;
typedef struct NODE Node;
typedef Node* PtrNode;
typedef PtrNode List;
typedef PtrNode Position;
typedef int DataType;

struct NODE{ // single link list node
DataType data;
PtrNode next;
};

PtrNode NewList() // returns the List's header
{
PtrNode tempNode =  malloc(sizeof(Node));
tempNode->next = NULL;
return tempNode;
}
Position NewNode() // creates a new node
{
return malloc(sizeof(Node));
}

void Delete(PtrNode node)// deletes the node
{
free(node);
}
BOOL IsLast(List L, Position pos) // checks id the given position is last in the list
{
return (pos->next == NULL);
}
void Insert ( List L, DataType data, Position pos)// inserts a data field in a particular position
{
Position tempPos;
tempPos = NewNode(); // creates and allocates memory space
if(tempPos == NULL)
{
fprintf(stderr, "error: request for allocation of memory using function \"malloc\" rejected");
return;
}
tempPos->data = data;
tempPos->next = pos->next;
pos->next = tempPos;
}

void DisplayElement(DataType element) // displays an individual element
{
printf("%d\n", element);
}
void Display (List L) // this function displays the list's contents linearly
{
Position pos = L->next;
if(pos == NULL)
return;
while (pos != NULL)
{
DisplayElement(pos->data);
pos = pos->next;
}
}

void SwapNodes(PtrNode preNode1, PtrNode preNode2) // swap the nodes connected to the passed on nodes
{
Position temp;
temp = preNode1->next; // first swaps the nodes as such
preNode1->next = preNode2->next;
preNode2->next = temp;

temp = preNode1->next->next; // now alter the swapped node's pointer links
preNode1->next->next = preNode2->next->next;
preNode2->next->next = temp;
}
void selectionSort(List L)
{
if(L->next == NULL || L->next->next == NULL)
return;
Position pos = L;
Position preMaxNode, preTempNode;
while(pos != NULL)
{
preTempNode = pos;
preMaxNode = pos;
while(!IsLast(L, preTempNode))
{
if(preMaxNode->next->data < preTempNode->next->data)
preMaxNode = preTempNode;
preTempNode = preTempNode->next;
}
if(!IsLast(L, pos)) // if the top is the last data field, no swapping is needed
SwapNodes(pos, preMaxNode);
pos = pos->next;
}

}

int main()
{
List L = NewList(); // creates a new list
int n, i, data;
Position top = L;
printf("enter size of list");
scanf("%d", &n);
if(n < 2 )
{
fprintf(stderr,"invalid list size. The size cannot be lesser than 2");
getch();
return -1;
}
printf("enter elements: ");
for(i=0; i<n; i++)
{
scanf("%d", &data); // creates the list
Insert(L, data, top);
top = top->next;
}
selectionSort(L); // sorts the list
printf("\nthe sorted elements:\n");
Display(L);
getch();
return 0;
}