C Programming Code Examples
C > Linked Lists Code Examples
Program to Find Intersection & Union of 2 Linked Lists
/* Program to Find Intersection & Union of 2 Linked Lists
This C Program finds the intersection and union of 2 linked lists. Intersection is a set of elements that are common in both lists while union is a set of all unique elements in both the lists */
#include <stdio.h>
#include <stdlib.h>
struct node
{
int j;
struct node *next;
};
void create(struct node **);
void findunion(struct node *, struct node *, struct node **);
void findintersect(struct node *, struct node *, struct node **);
void display(struct node *);
void release(struct node **);
int main()
{
struct node *phead, *qhead, *intersect, *unionlist;
phead = qhead = intersect = unionlist = NULL;
printf("Enter elements in the list 1\n");
create(&phead);
printf("\nEnter elements in the list 2\n");
create(&qhead);
findunion(phead, qhead, &unionlist);
findintersect(phead, qhead, &intersect);
printf("\nDisplaying list 1:\n");
display(phead);
printf("Displaying list 2:\n");
display(qhead);
printf("Displaying the union of the 2 lists:\n");
display(unionlist);
printf("Displaying the intersection of the 2 lists:\n");
if (intersect == NULL)
{
printf("Null\n");
}
else
{
display(intersect);
}
release(&phead);
release(&qhead);
release(&unionlist);
release(&intersect);
return 0;
}
void findintersect(struct node *p, struct node *q, struct node **intersect)
{
struct node *ptemp, *qtemp, *itemp, *irear, *ifront;
ptemp = p;
while (ptemp != NULL)
{
qtemp = q;
ifront = *intersect;
while (qtemp != NULL && ptemp->j != qtemp->j)
{
qtemp = qtemp->next;
}
if (qtemp != NULL)
{
if (ifront != NULL)
{
if (ifront->j == qtemp->j)
{
ptemp = ptemp->next;
continue;
}
ifront = ifront->next;
}
itemp = (struct node *)malloc(sizeof(struct node));
itemp->j = qtemp->j;
itemp->next = NULL;
if (*intersect == NULL)
{
*intersect = itemp;
}
else
{
irear->next = itemp;
}
irear = itemp;
}
ptemp = ptemp->next;
}
}
void findunion(struct node *p, struct node *q, struct node **unionlist)
{
struct node *utemp, *ufront, *urear;
int flag = 0;
while (p != NULL)
{
ufront = *unionlist;
while (ufront != NULL)
{
if (ufront->j == p->j)
{
flag = 1;
}
ufront = ufront->next;
}
if (flag)
{
flag = 0;
}
else
{
utemp = (struct node *)malloc(sizeof(struct node));
utemp->j = p->j;
utemp->next = NULL;
if (*unionlist == NULL)
{
*unionlist = utemp;
}
else
{
urear->next = utemp;
}
urear = utemp;
}
p = p->next;
}
while (q != NULL)
{
ufront = *unionlist;
while (ufront != NULL)
{
if (ufront->j == q->j)
{
flag = 1;
}
ufront = ufront->next;
}
if (flag)
{
flag = 0;
}
else
{
utemp = (struct node *)malloc(sizeof(struct node));
utemp->j = q->j;
utemp->next = NULL;
if (*unionlist == NULL)
{
*unionlist = utemp;
}
else
{
urear->next = utemp;
}
urear = utemp;
}
q = q->next;
}
}
void create(struct node **head)
{
struct node *temp, *rear;
int ch, a;
do
{
printf("Enter a number: ");
scanf("%d", &a);
temp = (struct node *)malloc(sizeof(struct node));
temp->j = a;
temp->next = NULL;
if (*head == NULL)
{
*head = temp;
}
else
{
rear->next = temp;
}
rear = temp;
printf("Do you want to continue [1/0] ? ");
scanf("%d", &ch);
} while (ch != 0);
}
void display(struct node *head)
{
while (head != NULL)
{
printf("%d ", head->j);
head = head->next;
}
printf("\n");
}
void release(struct node **head)
{
struct node *temp = *head;
while ((*head) != NULL)
{
(*head) = (*head)->next;
free (temp);
temp = *head;
}
}
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