ACPbE, Chpt3.2, ex3.6,Stacks and Queues
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#include <stdio.h>
#include <stdlib.h> // malloc() and exit()
#define EMPTY NULL
typedef struct node NODE;
struct node {
int i;
struct node *next;
};
// Stack Push()
NODE *pushs (NODE *stack, int i)
{
NODE *new ;
if ((new = (NODE *) malloc( sizeof(NODE))) == NULL)
{
printf ("errFATAL, malloc() in pushs!\n");
exit (1);
}
new->i = i ;
new->next = stack ;
stack = new ;
return stack ;
}
NODE *pops( NODE **stack)
{
NODE *first;
if (*stack == NULL) return NULL;
first = *stack ;
*stack = (*stack)->next;
first->next = NULL ;
return first;
}
// Queue push
void pushq (NODE **q, NODE **rear, int i)
{
NODE *new ;
if ((new = (NODE *)malloc(sizeof(NODE))) == NULL)
{
printf ("errFATAL, malloc in pushq()\n");
exit (1);
}
new->i = i ;
new->next = NULL ;
if (*q == NULL) *q = new ; // no q add item
else (*rear)->next = new ; // update (*rear)->next, queue
*rear = new ;
}
NODE *popq (NODE **q, NODE **rear)
{
NODE *first ;
first = *q ;
if (*q == NULL) return NULL ; //empty Q, nothing to pop
*q = (*q)->next ;
if (*q == NULL) *rear = NULL;
first->next = NULL ;
return first ;
}
// driver program for stack and queue
int main(void)
{
NODE *stack = NULL, *q = NULL, *rear = NULL, *top;
NODE *pushs (NODE *stack, int i), *pops(NODE **stack),
*popq (NODE **q, NODE **rear);
void pushq (NODE **q, NODE **rear, int i);
// Begin stack testing
stack = pushs (stack, 3) ;
stack = pushs (stack, 4) ;
stack = pushs (stack, 5) ;
top = pops (&stack) ;
printf ("Top node of stack is %d\n", top ? top->i : EMPTY ) ;
top = pops (&stack) ;
printf ("Top node of stack is %d\n", top ? top->i : EMPTY ) ;
top = pops (&stack) ;
printf ("Top node of stack is %d\n", top ? top->i : EMPTY ) ;
// Beginning queue driver
pushq (&q, &rear, 3) ;
pushq (&q, &rear, 4) ;
pushq (&q, &rear, 5) ;
top = popq (&q, &rear) ;
printf ("Top node of queue is %d\n", top ? top->i : EMPTY) ;
top = popq (&q, &rear) ;
printf ("Top node of queue is %d\n", top ? top->i : EMPTY) ;
top = popq (&q, &rear) ;
printf ("Top node of queue is %d\n", top ? top->i : EMPTY) ;
top = popq (&q, &rear) ;
printf ("Top node of queue is %d\n", top ? top->i : EMPTY) ;
printf("Hello World!\n");
return 0;
}
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