Skip to content

Instantly share code, notes, and snippets.

@vinay13
Created August 10, 2014 14:44
Show Gist options
  • Save vinay13/4ff40132a1a99b7b4780 to your computer and use it in GitHub Desktop.
Save vinay13/4ff40132a1a99b7b4780 to your computer and use it in GitHub Desktop.
queue 2 stack
#include<stdio.h>
#include<stdlib.h>
/* structure of a stack node */
struct sNode
{
int data;
struct sNode *next;
};
/* structure of queue having two stacks */
struct queue
{
struct sNode *stack1;
};
/* Function to push an item to stack*/
void push(struct sNode** top_ref, int new_data);
/* Function to pop an item from stack*/
int pop(struct sNode** top_ref);
/* Function to enqueue an item to queue */
void enQueue(struct queue *q, int x)
{
push(&q->stack1, x);
}
/* Function to dequeue an item from queue */
int deQueue(struct queue *q)
{
int x, res;
/* If both stacks are empty then error */
if(q->stack1 == NULL)
{
printf("Q is empty");
getchar();
exit(0);
}
else if(q->stack1->next == NULL)
{
return pop(&q->stack1);
}
else
{
/* pop an item from the stack1 */
x = pop(&q->stack1);
/* store the last dequeued item */
res = deQueue(q);
/* push everything back to stack1 */
push(&q->stack1, x);
return res;
}
}
/* Function to push an item to stack*/
void push(struct sNode** top_ref, int new_data)
{
/* allocate node */
struct sNode* new_node =
(struct sNode*) malloc(sizeof(struct sNode));
if(new_node == NULL)
{
printf("Stack overflow \n");
getchar();
exit(0);
}
/* put in the data */
new_node->data = new_data;
/* link the old list off the new node */
new_node->next = (*top_ref);
/* move the head to point to the new node */
(*top_ref) = new_node;
}
/* Function to pop an item from stack*/
int pop(struct sNode** top_ref)
{
int res;
struct sNode *top;
/*If stack is empty then error */
if(*top_ref == NULL)
{
printf("Stack overflow \n");
getchar();
exit(0);
}
else
{
top = *top_ref;
res = top->data;
*top_ref = top->next;
free(top);
return res;
}
}
/* Driver function to test above functions */
int main()
{
/* Create a queue with items 1 2 3*/
struct queue *q = (struct queue*)malloc(sizeof(struct queue));
q->stack1 = NULL;
enQueue(q, 1);
enQueue(q, 2);
enQueue(q, 3);
/* Dequeue items */
printf("%d ", deQueue(q));
printf("%d ", deQueue(q));
printf("%d ", deQueue(q));
getchar();
}
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment