C/C++ Source Codes

programme on implementation on queue

//queue
#include <stdio.h>
#include <string.h>
#include <stdlib.h>

struct Queue{
struct Queue *node;
char item[1];
};
struct Queue *volatile q;
int QueueAdd(const char *_item)
{
int _q;
struct Queue *queue;
_q = sizeof(struct Queue) + strlen(_item) + 4;
queue = (struct Queue *)malloc(_q); /* allocate the space in memory we need */
if (queue == 0) return 1;
memset(queue, 0, _q);
strcpy(queue->item, _item);
queue->node = q;
q = queue;

return 0;
}
void printq()
{
struct Queue *qq;

int n,j,num;
n=0;
for (qq=q, num=0; qq; qq=qq->node, num++); /* enumerate items in queue */
if(num==NULL)
{
printf("No items currently in the Queue");
return;
}
printf("Here are the items in the Queue \n");
cycle:
for (j=0,qq=q; (j < n) && qq; qq=qq->node, j++); /* lets hop to the next node */
printf("%s \n",qq->item);
n++;
if(n<num)
goto cycle;
}
int main()
{
struct Queue *qq;
int i,num;
char in[100]; /* array of 100 bytes */
/* print to stdout */
printf("Welcome to the Queue!");
printf("\n Dequeue not implemented \n");
printf("Usage: \n");
input: /* input label */
printf("\n1. Add to the queue\n");
printf("2. Print number of items in Queue \n");
printf("3. Print the items in the Queue \n");
printf("4. Exit the program \n");

scanf("%d",&i); /* check for inputted data */
switch(i)
{
case 1:
printf("Enter Item to add to the Queue \n");
scanf("%s",&in);

QueueAdd(in); /* call 'QueueAdd', let us assume everything goes o.k. */
printf("%s successfully added to the queue",in);
goto input;
break;
case 2:
for (qq=q, num=0; qq; qq=qq->node, num++);
/* Null statement above to enumerate items in the queue */
printf("There are %d items in the queue",num);
goto input;
break;
case 3:
printq();
goto input;
break;
case 4:
printf("Exiting program");
exit(0);
break; /* why not? :) */

default:
printf("Tu esta estupido!");
goto input;
}
}

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