Algorithm 5.5 (Insert Item in nth Position in Linked List)

Before seeing the solution make sure that you tried enough. Don’t paste the whole code, just find out the logic. If you stuck in trouble, just inform me on comment.

/**Bismillahir Rahmanir Rahim.**/

#include <stdio.h>
#include <stdlib.h>
int m=1, i, x, n, nth;
struct node
{
    int info;
    struct node* ptr;
};

struct node* start;
struct node* temp1;
struct node* temp2;

void insert(int x)
{
    temp1 = (struct node*) malloc(sizeof(struct node));
    temp1->info = x;
    temp1->ptr = NULL;
    if(m==1)
    {
        temp1->ptr = NULL;
        start = temp1;
        temp2 = temp1;
        m = 0;
        return ;
    }
    temp2->ptr = temp1;
    temp2 = temp1;
}
void insert_first()
{
    scanf("%d", &x);
    temp1 = (struct node*) malloc(sizeof(struct node));
    temp1->info = x;

    temp1->ptr = start;
    start = temp1;
}

void insert_nth()
{
    scanf("%d", &nth);
    printf("Insert what you want to insert........\n");
    if(nth==1)
    {
        insert_first();
        return;
    }
    scanf("%d", &x);
    temp1 = (struct node*) malloc(sizeof(struct node));
    temp1->info = x;
    temp2 = start;
    for(i=0; i<nth-2; i++)
        temp2 = temp2->ptr;

    temp1->ptr = temp2->ptr;
    temp2->ptr = temp1;
}

void print()
{
    temp1 = start;
    printf("List is: ");
    while(temp1 != NULL)
    {
        printf(" %d ", temp1->info);
        temp1 = temp1->ptr;
    }
    printf("\n");
    free(temp1);
}
int main()
{
    start = NULL;
    printf("How Many Node??\n");
    scanf("%d", &n);
    printf("Print %d node :: \n", n);
    for(i=0; i<n; i++)
    {
        scanf("%d", &x);
        insert(x);
    }
    printf("In which node you want to Insert....\n");
    insert_nth();
    print();
    free(temp1);
    return 0;
}

First Input n = number of Total Node.  ex.   4.
second Input n node item . ex.     10  30  40  50.
In which node i want to insert. ex. 2.
What i want to insert.   20

Sample Input:
------------------
4
10 30 40 50
2
20
sample Output:
---------------------
List is : 10 20 30 40 50