#include 
     
      #include 
      
       typedef int queue_element_t;typedef struct queue_node_s{    queue_element_t element;    struct queue_node_s *restp;}queue_node_t;/*Queue front & rear pointer*/typedef struct{    queue_node_t *frontp,             *rearp;    int size;         }queue_t;void add_to_q(queue_t *qp, queue_element_t ele){    /*Keep queue front pointer*/    if(qp->size == 0)    {        qp->rearp = (queue_node_t*)malloc(sizeof(queue_node_t));        qp->frontp = qp->rearp;    }    /*Renew queue rear pointer*/    else    {        qp->rearp->restp = (queue_node_t*)malloc(sizeof(queue_node_t));        qp->rearp = qp->rearp->restp;    }        qp->rearp->element = ele;    qp->rearp->restp = NULL;    ++(qp->size);}queue_element_t remove_from_q(queue_t *qp){    queue_node_t *to_freep;    queue_element_t ans;        to_freep = qp->frontp;    ans = to_freep->element;    qp->frontp = to_freep->restp;    free(to_freep);    --(qp->size);        if(qp->size == 0)        qp->rearp = NULL;            return ans;    }int main(void){    queue_t queue = {NULL, NULL, 0};        add_to_q(&queue, 100);    add_to_q(&queue, 200);    add_to_q(&queue, 300);    add_to_q(&queue, 400);    int i;    int sum = queue.size;        for(i = 0; i < sum; i++)        printf("%d\n", remove_from_q(&queue));}